Former Enron chairman Kenneth Lay sold some $70 million of his Enron stock back to the company to repay loans last year, including $16.3 million in the 13 days after he was warned by executive Sherron Watkins of serious accounting problems, an official document shows.

Lay frequently sold blocks of shares — many worth as much as $4 million — from February through October, a period in which the big energy-trading company's stock tumbled from around $78 a share to about $15.

Houston-based Enron Corp. entered the biggest bankruptcy in U.S. history on Dec. 2 after questions arose about its use of a complex web of partnerships that hid more than $1 billion in debt from investors and securities regulators.

Some of the sales came at a time when Lay was touting Enron's stock and future prospects to employees, assuring them that the company's finances were sound and its books in good shape. "The third quarter is looking great," he messaged an employee on Sept. 26. He had sold $4 million worth of stock to the company on Sept. 4.

Documents released Friday in Austin, Texas, meanwhile, show that Lay wrote repeatedly to George W. Bush throughout his governorship, seeking support for legislation benefiting Enron. Many of the letters concerned electricity deregulation and an overhaul of laws to make it harder to bring lawsuits. Others were personal.

Lay, who this week asserted his Fifth Amendment right against self-incrimination and refused to testify before Congress, had not previously made the stock-sale information public. He filed it with the Securities and Exchange Commission, as he was required to do this week under a special rule giving officers and directors who make such stock sales to their companies more than a year to disclose them. A copy was provided Friday by his representative.

Added to sales of Enron shares on the open market which he had previously reported, the new filing shows that Lay sold around $100 million of company stock in 2001.

"Mr. Lay remained confident in Enron stock through late 2001," his spokeswoman, Kelly Kimberly, said from Houston. She noted that he was entitled to borrow money from Enron under an agreement, "and he exercised that benefit."

Lay was "surprised" by the rapid decline in the stock, which was his collateral for the loans, Kimberly said, adding that "the vast majority of the proceeds" from the sales went to repay the loans.

Watkins, an accountant who worked in the Enron division that ran the questionable partnerships, warned Lay in a detailed, six-page memo on Aug. 22 that the company could "implode in a wave of accounting scandals."

The next day, Lay's new SEC filing shows, he sold 108,254 Enron shares back to the company at $36.95 each, a transaction worth around $4 million. He followed up with similar amounts on Aug. 24, Aug. 30 and Sept. 4. His next sale of shares to the company, for $1.5 million, wasn't until Oct. 23 — a week after Enron shocked investors by reporting more than $600 million in losses for the third quarter, prompting an SEC inquiry. By then the stock had fallen to $19.79 a share.

Lay, who resigned Jan. 23, told internal company investigators that he thought the partnerships and transactions involving them were proper because Enron's longtime auditing firm, Arthur Andersen LLP, had signed off on them.

The Justice Department and the SEC are investigating Enron's collapse and the role of Andersen, which has acknowledged massive destruction by its employees of Enron-related documents.

Lay's wife, Linda, defended him in a television interview last month and said he was largely misled by subordinates. She said they were struggling to avoid personal bankruptcy because "Everything we had mostly was in Enron stock. ... Virtually — other than the home we live in — everything we own is for sale."

William Powers, the former Enron director and University of Texas Law School dean who headed the internal investigation, has said that Lay "bears significant responsibility ... for Enron's failure to implement sufficiently rigorous procedural controls to prevent the abuses."