Updated from July 7

Kenneth Lay, the indicted former chairman of Enron, turned himself into authorities in Houston Thursday, capping more than two years of prosecutorial pursuit in America's most notorious corporate collapse.

Lay, Enron's well-connected architect whose aloof manner infuriated investors as the energy trader sank into insolvency, was handcuffed and taken by FBI agents to a federal courthouse, where he is expected to be arraigned on criminal charges including insider trading.

According to a source, the charges will be similar to those filed in February against Jeffery Skilling, Enron's former chief executive, who was indicted on securities fraud and insider trading charges. The Securities and Exchange Commission also is expected to file civil charges against Lay along with the criminal charges being brought by the Justice Department's Enron Task Force.

Michael Ramsey, Lay's lawyer, could not be reached for comment.

The indictment of Lay marks the final step in a march up the corporate ladder that began in August 2003 with a guilty plea from Michael Kopper to money-laundering and conspiracy charges. Kopper was the right-hand man to Andrew Fastow, the former Enron chief financial officer, who masterminded the off balance sheet accounting tricks used to inflate earnings and hide its assets.

The indictment is also a rebuke to critics who said prosecutors would never touch Lay, who refused to testify when called before Congress shortly after Enron filed for bankruptcy in December 2001. Lay asserted his Fifth Amendment right against self-incrimination and has said little since. He claims to be innocent of criminal wrongdoing in the storied collapse.

Lay's armor cracked earlier this year when prosecutors reached a plea agreement with Fastow. That led to the indictment of Richard Causey, Enron's former chief accounting officer. Soon after, Skilling was added as a defendant in a superseding indictment. Both Causey and Skilling have pleaded not guilty to the charges.

Federal authorities contend that both Skilling and Causey knew by the fourth quarter of 1999 that Enron was not meeting its budget targets and that the company only appeared to be profitable because of the many schemes they and others concocted to juice reported earnings. The two men specifically are charged with concealing large losses in two of the company's divisions: Enron Broadband Services and Enron Energy Services.

The SEC, meanwhile, has charged Skilling will selling Enron stock while in possession of material, nonpublic information, generating unlawful proceeds of about $63 million.

Last November, a special examiner in the Enron bankruptcy proceeding concluded that both Lay and Skilling most likely knew some of Enron's financial officers were misusing the company's array of off balance sheet entities and providing the public with misleading financial information.

The examiner suggested that Enron's former top managers might have to repay loans to the fallen oil- and gas-trading firm. Between May 1999 and October 2001, Lay borrowed more than $94 million from Enron and repaid it with company stock. In May 1999, Skilling repaid $2 million with Enron stock

The Enron corporate fraud is notable because it goes beyond a mere accounting scandal that catches a few rogue executives.

To date, a number of investment bankers, including three former Merrill Lynch ( MER) bankers, were charged with aiding and abetting the company's fraud.

The SEC also has levied steep fines against Merrill, Citigroup ( C), J.P. Morgan Chase ( JPM) and Canadian Imperial Bank of Commerce ( BCM) for their role in helping to finance Enron's shady accounting schemes.

Enron's former auditor, Arthur Andersen, was forced to close its doors, after a federal jury convicted the giant accounting firm of an obstruction of justice charge early on in the investigation. .