Negotiations with the Justice Department about the activities of the Arthur Andersen accounting firm after the spectacular collapse of Enron Corp. are expected to peak as early as Thursday when a top U.S. prosecutor returns from overseas.

Andersen lawyers have been negotiating off and on with the Justice Department since last week to determine whether the firm could avoid criminal charges in the Enron case. But U.S. officials have indicated that no formal decision is anticipated until Thursday, when Michael Chertoff, head of the department's criminal division, is back in his office from a trip with Attorney General John Ashcroft to Trinidad.

The two sides have agreed to continue discussions this week, a source familiar with the talks said Tuesday, speaking on condition of anonymity.

Andersen already has publicly acknowledged massive shredding by its employees of Enron-related documents. Enron was the world's largest buyer and seller of natural gas, growing into the nation's seventh-largest company and a Wall Street favorite as the country's leading electricity trader.

Meanwhile, the Commodity Futures Trading Commission is looking into whether Enron committed fraud or manipulated markets with improper trading.

"We do have a full investigation under way," CFTC Chairman James Newsome said Monday in a telephone interview, noting that the agency is using its anti-fraud and anti-manipulation authority to investigate Enron's trading on commodity exchanges, notably the New York Mercantile Exchange, as well as its own big online trading system.

The Enron system, called EnronOnline, was the world's first commodity trading platform based on the Web.

The Houston-based company later started new trading markets in telecommunications bandwidth, pulp, paper, plastics and the influence of the weather. Enron spiraled downward into the biggest corporate bankruptcy in U.S. history on Dec. 2.

Word of the commodities trading investigation, first reported by The Wall Street Journal, comes as Enron's longtime auditor, the Arthur Andersen accounting firm, negotiates with federal prosecutors over whether it can avoid criminal charges in the Enron case.

Enron spokesmen had no immediate comment on the CFTC investigation.

The Justice Department, the Securities and Exchange Commission and a dozen congressional committees are investigating Enron, its accounting practices and Andersen's role. In addition, the Federal Energy Regulatory Commission is examining possible energy price manipulation by Enron and other traders in Western wholesale power markets.

The Labor Department, meanwhile, is investigating Enron's actions in banning employees -- who lost their retirement savings -- from selling company stock in their 401(k) plans for about three weeks.

Wendy Gramm, an Enron director and member of the board's audit committee, was chairwoman of the CFTC before she joined the Enron board in 1993. As head of the agency, she shepherded an exemption from government oversight for the trading of energy products, which benefited Enron and other energy-trading companies. Gramm, an economist, is married to Sen. Phil Gramm, R-Texas, former chairman of the Senate Banking Committee.

Under current law, the CFTC doesn't have the authority to regulate over-the-counter or electronic derivatives trading but is empowered to investigate if it suspects fraud or market manipulation.