Former Enron chairman Kenneth Lay, who was convicted of fraud and conspiracy for his part in the energy giant's collapse, has died of a heart attack.

Lay, who was 64, collapsed at his vacation home in Aspen, Colorado, early Wednesday morning, the Colorado Sheriff's Department said.

Officers were called to Lay's house shortly after 1 a.m. Mountain time and he was taken to Aspen Valley Hospital, where he was pronounced dead at 3:11 a.m.

Family spokeswoman Kelly L. Kimberly issued a statement saying: "Ken Lay passed away early this morning in Aspen. The Lays have a very large family with whom they need to communicate. And out of respect for the family, we will release further details at a later time."

Pastor Steve Wende of First United Methodist Church of Houston, said in a statement that church member Lay died unexpectedly of a "massive coronary."

Wende said Lay and his wife Linda were in Colorado for the week "and his death was totally unexpected. Apparently, his heart simply gave out."

Guilty

Lay and Enron's former chief executive Jeffrey Skilling were found guilty on May 25 in one of the biggest corporate scandals in U.S. history.

Both men were free on bail, each having managed to secure a $5-million US bond.

Lay was convicted on all six counts against him, including conspiracy to commit securities and wire fraud, and faced up to 45 years in prison. He was due to be sentenced in October.

Skilling was found guilty of 19 out of 28 counts of conspiracy, fraud, insider trading and making false statements. Combined, these carry a maximum sentence of 185 years. He was not convicted on the remaining nine criminal counts.

Both were accused of repeatedly lying to investors and employees about Enron's finances before its spectacular December 2001 collapse into bankruptcy.

Lay and Skilling denied any wrongdoing and attributed the Houston-based company's failure to bad publicity and lost market confidence triggered by revelations that Enron chief's financial officer Andrew Fastow had stolen millions from the company.

In a separate trial, Lay was also convicted of illegally using money from $75 million US in personal loans to buy stock. He faced a maximum of 120 years in prison for that conviction, in addition to the 45 years for the corporate trial.

"We fought a good fight and some things work, some things don't," Skilling said in a brief statement outside court during which he thanked his family and his lawyer.

"We're going to have to go back and think this thing through. Obviously I'm disappointed but that's the way the system works."

Lay made a separate statement, saying he was "shocked" by the jury's decision and denied any wrongdoing.

"I firmly believe I'm innocent of the charges against me as I have said from day one, and I still firmly believe that to this day," Lay told reporters outside the court.

Bankrupt

For many years, Enron was the single biggest contributor to U.S President George W. Bush, who nicknamed Lay "Kenny Boy."

Enron collapsed after it was revealed the company's finances were based on a web of fraudulent partnerships and schemes, not the profits that it reported to investors and the public.

It went bankrupt in 2001 with debts of $31.8 billion US, leaving 4,000 people out of work.

When Lay and Skilling went on trial on Jan. 30, 2006, it had been expected that Lay, who enjoyed great popularity throughout Houston, might be able to charm the jury.

But during his testimony, Lay ended up coming across as irritable and combative.

He also sounded arrogant, defending his extravagant lifestyle despite $100 million in personal debt, saying "it was difficult to turn off that lifestyle like a spigot."

Humble beginnings

Lay was born in Tyrone, Mo. where his father ran a general store and sold stoves until he became a minister. Lay delivered newspapers and mowed lawns to help out.

He attended the University of Missouri where he found his calling in economics and went to work at Exxon Mobil Corp. upon graduation.

After joining the Navy, Lay served his time at the Pentagon and then served as undersecretary for the Department of the Interior before he returned to business where he became an executive at Florida Gas, then Transco Energy in Houston, and later became CEO of Houston Natural Gas.

In 1985, HNG merged with InterNorth in Omaha, Neb. to form Enron, and Lay became chairman and CEO of the combined company the following year.

He led the company for 15 years until 2001, when he handed over the chief executive's job to Skilling.

Lay described Enron's collapse as "the most devastating and heartbreaking tragedy of my life".

With files from the Associated Press