Joe Dunn, a California state senator, said on Wednesday that he would request subpoenas demanding that executives from Enron and its accountant, Arthur Andersen, give depositions about destroyed documents.

Officials of the auditing company, Arthur Andersen, sought guidance from their lawyers then about how to respond, according to the investigators. The disclosure raised fresh questions about Andersen's decision to stand by Enron's financial reports until early November, when the accountants forced the company — by then under investigation by the Securities and Exchange Commission — to restate five years of results and erase almost $600 million in reported profits.

Also, a February 2001 Andersen e- mail message obtained by Congressional investigators indicates that some senior Andersen officials discussed dropping Enron as a client nearly one year ago because of concerns about Enron's accounting, the investigators said. An Andersen spokesman tonight declined to comment on the message.

In Washington today, the White House disclosed that Lawrence B. Lindsey, who is President Bush's top economic adviser and head of the National Economic Council, had overseen a study in mid-October of how a collapse of Enron would affect the economy.

According to Congressional investigators, the Enron employee, Sherron S. Watkins, called a former colleague at Andersen on Aug. 20 and told him of her concerns about the energy company's accounting. About the same time, Ms. Watkins also laid out her doubts in a letter to Enron's chairman, Kenneth L. Lay, disclosed earlier this week by a Congressional committee, that warned that the company might be revealed as an "elaborate accounting hoax."

Ms. Watkins's letter pointed to new questions about Enron's web of partnerships and raised the possibility that the company might have to reduce past earnings by $1.3 billion more than it already has. [Business Day, Page C1.]

In an internal Andersen memorandum obtained by the House Energy and Commerce Committee, Ms. Watkins's former colleague at Andersen wrote that "based on our discussion I told her she appeared to have some good questions."

On the next day, Aug. 21, four Andersen officials met to discuss Ms. Watkins's concerns, investigators said. They included David B. Duncan, the lead partner on the Enron account, whom Andersen fired this week after saying he ordered the destruction of Enron documents while the company's accounting was under investigation by the S.E.C.

The officials then "agreed to consult with our firm's legal adviser about what actions to take in response to Sherron's discussion of potential accounting and disclosure issues," according to the memo.

Investigators say Andersen began the destruction of Enron documents in September and that an e-mail message from an Andersen lawyer on Oct. 12 re-emphasized Andersen's policy on destroying documents and encouraged the activity in the firm's Houston office.

Mr. Duncan, who is cooperating with authorities, spent hours in Washington today with government officials who are investigating the failure of Enron, the Houston company that pioneered energy deregulation and grew to be the nation's seventh-largest company before seeking bankruptcy protection last fall.

He met for the second time this week with officials from the Justice Department, which is conducting a criminal investigation of Enron's collapse. On Monday — the day before Andersen fired him — Mr. Duncan met with Justice Department officials as well as staff members from the S.E.C. and agents from the F.B.I., according to people close to the inquiries.

This afternoon, he spent more than four hours answering questions from eight investigators for the House Energy and Commerce Committee, one of several panels in Congress reviewing Enron's demise. Flanked by his lawyers, Mr. Duncan was not sworn, but he was warned not to give false statements to Congress. There was no discussion of giving him immunity for his testimony, investigators said.

"He answered our questions and provided us with some valuable information, which we are pursuing," said Ken Johnson, a spokesman for Representative Billy Tauzin, a Louisiana Republican and chairman of the committee. Mr. Johnson declined to comment in detail about the interview but said that Andersen's shredding of documents and handling of the Enron account were discussed.

Sullivan & Cromwell, the law firm representing Mr. Duncan, released a statement that said he was "continuing to cooperate with all investigations of this matter, and he looks forward to full disclosure of the truth."

Laura Sheehan, the spokeswoman for the energy panel's Democratic members, said that investigators had hoped to learn more from Mr. Duncan. "Our investigators were disappointed by the limited nature of Mr. Duncan's memory," she said. "We expect documents and other witnesses to fill in the blanks."

Mr. Johnson said that the Andersen memo about Ms. Watkins's concerns suggested that the firm was well aware that Enron's accounting was suspect long before the company had disclosed its problems.

"It's clear now to us that key players at both Enron and Andersen knew of the problems months before the company imploded," Mr. Johnson said.

Representative James C. Greenwood, a Republican from Pennsylvania who heads the committee's oversight and investigation subcommittee, said the internal Andersen memo "raises additional concerns about Andersen's knowledge of potential accounting irregularities and the subsequent destruction of Enron- related documents."

A spokesman for Andersen, Charlie Leonard, said he did not know who was contacted at Andersen, which is based in Chicago, by officials in the firm's Houston office after their meeting about Ms. Watkins's concerns. He said the firm had contacted Mr. Lay and Enron's general counsel, James Derrick, about the matter. Andersen was told that Vinson & Elkins, a Houston law firm that represents Enron, was being brought in to review Ms. Watkins's concerns.

Mr. Leonard said he did not know who at Andersen, other than Mr. Duncan, had participated in the Aug. 21 meeting. In addition to firing Mr. Duncan, Andersen this week placed on leave three other partners who worked on the Enron account, and the firm took away management responsibilities from four other partners in the Houston office.

According to a person close to the case, Mr. Duncan told investigators that he disposed of documents in keeping with the Oct. 12 e-mail message from an Andersen lawyer in Chicago and that the destruction stopped when the lawyer left a voice mail message at the Houston office on Nov. 9.

Andersen said on Tuesday that Mr. Duncan had ordered "an expedited effort to destroy documents" on Oct. 23, the day after Enron disclosed that the S.E.C. had begun its inquiry. The firm said the destruction apparently did not end until Mr. Duncan's assistant sent an e-mail message to other secretaries on Nov. 9 that said "stop the shredding."

Much of Mr. Duncan's discussion with investigators focused on the documents that were destroyed and on Enron's restatement of earnings in early November, the person close to the case said.

Also today, a senior Treasury Department official said that the nation's accounting and corporate disclosure rules needed to be strengthened. Speaking to a gathering of the American Council of Life Insurers in Boca Raton, Fla., Peter R. Fisher, the Treasury under secretary for domestic finance, alluded to Enron's collapse and cited "the failure of our financial accounting and disclosure practices to keep pace with the rapid evolution of our capital markets and corporate finance."

The Treasury Department disclosed last week that Enron's president repeatedly called Mr. Fisher in late October and early November seeking his help arranging bank loans as Enron scrambled to avoid collapse. Mr. Fisher — who also was called by Robert E. Rubin, a former Treasury secretary whose current company, Citigroup (news/quote), was one of Enron's lead bankers — has said that he took no action on the company's behalf.

Two senior Democratic lawmakers, meanwhile, raised concerns about possible conflicts of interest at the Justice Department in the Enron investigation.

Representative John Conyers of Michigan, the ranking Democrat on the House Judiciary Committee, suggested that Deputy Attorney General Larry Thompson — who is ultimately in charge of the criminal investigation — could have a conflict because his former law firm, King & Spalding, had represented Enron.

Also, Senator Patrick J. Leahy of Vermont, chairman of the Judiciary Committee, questioned whether a conflict existed because Andersen was also working on an F.B.I. reorganization.

Mr. Thompson told reporters that while his old firm had done work for Enron, he never had. He also said the Andersen unit doing the F.B.I. review was separate from Andersen's accounting business. Last week, Attorney General John Ashcroft, who received campaign contributions from Enron while serving in the Senate, recused himself from the case.

New details also emerged today concerning Enron workers' losses in their 401(k) plans. A lawyer for employees suing over the 401(k) losses released two internal Enron e-mail messages detailing the timing of a "lockdown" during October and November, during which employees could not sell Enron shares in their accounts.

Enron has maintained that the lockdown did not begin until Oct. 29 and lasted only 10 trading days — a period in which the stock fell $3.83. Enron has also said that employees were notified of these dates in an Oct. 4 mailing to their homes.

But the e-mail messages released by Eli Gottesdiener, a lawyer in Washington, who represents some employees, include a Sept. 27 message to all employees that the lockdown would begin on Oct. 19 and last about a month. A second message, dated Oct. 25, said that the lockdown would last from Oct. 26 to Nov. 20 and acknowledged employees' fears about the company's deteriorating condition.

Mr. Gottesdiener argued that the e-mail also showed that many employees were misled to believe the lockdown started a week before it actually did — leading them not to sell shares in a week in which the stock fell $10.65. Enron shares, which were above $90 in August 2000, are now worth less than $1.

On average, Enron employees had more than 60 percent of their 401(k) plans invested in Enron stock, and many have lost their savings in the wake of the company's collapse. Several lawmakers say the company improperly forced workers to hold their stock as the company faltered and have proposed legislative changes to restrict such lockdowns.

Meanwhile, Joe Dunn, a Democratic California state senator leading an investigation of possible electricity-price manipulation during the state's energy crisis last year said some documents destroyed by Andersen were possibly subject to a subpoena issued last summer by his legislative committee. Tonight, Andersen said the firm had no reason to believe that anything related to the California subpoena was destroyed.