A federal grand jury in Houston indicted Andrew S. Fastow, the former chief financial officer of Enron Corp., yesterday on dozens of fraud, money-laundering and conspiracy charges, the latest move in the active government probe into wrongdoing at the bankrupt energy trader.

The charges against Fastow, who allegedly masterminded a complex web of partnerships that disguised Enron's financial woes and funneled millions of dollars into his own pockets, were filed four weeks after he surrendered to the FBI and was released on a $5 million bond. He is the highest-ranking Enron official to face criminal charges.

The 78-count indictment closely tracks allegations that prosecutors leveled against Fastow in a sworn statement by an FBI agent at that time. The court papers also include a new claim: that Fastow attempted to block investigators by persuading his top aide, Michael J. Kopper, to tamper with laptop and desktop computers late in the summer of 2001. That was shortly after Enron executive Sherron Watkins raised questions about Enron's accounting practices but before the company's financial woes became public.

The obstruction count is significant because it challenges Fastow's claim, as cited by his attorney, John W. Keker, that he "never believed he was committing any crime."

"The natural question is, why would you try to influence someone to cover up or destroy evidence if you thought you did nothing wrong?" said Thomas R. Ajamie, a Houston defense lawyer. "That's a question the jury will face."

Fastow, 40, is scheduled to appear in a Houston courtroom Wednesday to enter a formal plea on the charges. He faces up to 20 years in prison under the money-laundering counts alone.

Andrew Weissmann, deputy director of the Justice Department's Enron task force, said outside the courthouse yesterday that Fastow is not cooperating with prosecutors or providing evidence about other Enron misdeeds. Asked whether the potential for steep fines and prison time would induce the defendant to change his mind, Weissmann said, "If you do the math . . . these are significant charges that carry significant jail terms."

Keker said in a statement: "These charges are full of sound and fury, but the truth about Enron has yet to be told. When that truth is told, to a jury of 12 honest Americans, Andy Fastow will be set free."

Deputy Attorney General Larry D. Thompson said: "The investigation into Fastow's illegal activities continues. We will use every appropriate measure to recover the ill-gotten gains of these corporate schemers."

In a sign of the continuing investigation, the same Houston grand jury heard testimony last week about Enron stock sales by former chairman Kenneth L. Lay before the company's collapse, according to lawyers involved in the case. Michael R. Ramsey, a lawyer representing Lay, said his client behaved appropriately when he sold Enron shares.

Enron's collapse has had far-reaching effects, leading to massive shareholder losses and thousands of job cuts. Enron, which is attempting to reorganize out of bankruptcy, is defending itself against civil lawsuits filed by investors and lenders.

Starting in 1997, according to court papers, Fastow and others devised a plan to use bookkeeping maneuvers to hide the company's financial trouble, inflate its stock price, avoid federal energy regulations and enrich themselves by tens of millions of dollars.

Fastow and his business associates -- many of whom are not named in court papers because of a Justice Department policy not to name people it has not criminally charged -- used scores of secretive off-balance-sheet partnerships to achieve those goals.

The indictment cited evidence about myriad transfers of allegedly tainted funds to Fastow, his wife, his two sons and other former associates, including onetime Enron in-house lawyer Kristina Mordaunt, former treasurer Ben F. Glisan Jr. and partnership employee Michael Hinds.

After an August guilty plea by Kopper, Fastow's right-hand man, the Enron task force moved to seize more than $20 million in bank accounts belonging to Fastow and his wife. Prosecutors also successfully sought to place in escrow about $4 million in proceeds from the sale of the family's new house in a luxurious Houston neighborhood.

Kopper, a key government witness, told a judge at his plea hearing that he kicked back thousands of dollars to Fastow and his relatives. Kopper also described the inner workings of the partnerships he and Fastow controlled -- and apparently shared information about Fastow's alleged attempts to persuade Kopper to tamper with Enron computers.

Earlier this month, prosecutors used a detailed criminal complaint to lay out their case against Fastow and send a signal to other former Enron executives who allegedly helped obscure the company's financial problems, including former chief accounting officer Richard A. Causey and former treasurer Jeffrey McMahon. The complaint and yesterday's indictment also cited an unnamed "major financial institution," which congressional testimony disclosed is Merrill Lynch & Co., that helped Enron to book profits in an alleged sham energy deal in late 1999.

Attorneys for Causey and McMahon did not return calls. A spokesman for Merrill Lynch has said that its employees did nothing wrong in their dealings with Enron and that Enron is responsible for how it treated the deal on its books.

Special correspondent Aaron Katersky in Houston contributed to this report.