Enron ex-chairman Kenneth Lay has been indicted in connection with the 2001 collapse of the former US energy giant.
Mr Lay, who is due to before a Houston court on Thursday, said he had done nothing wrong, and that the indictment was "not justified".
Details of the charges against him are contained in sealed indictments and will not be disclosed until then.
Prosecutors have been trying to build a case against Mr Lay for over two years and his indictment had been expected.
In June Mr Lay blamed the fraud on his chief financial officer, Andrew Fastow.
Ultimate responsibility
On Wednesday, the 62-year-old former Enron chairman said he had been notified of the indictment and would surrender early on Thursday.
The firm went bankrupt in December 2001 after it emerged that the company had concealed millions of dollars in debts.
Mr Fastow had devised complex partnerships to hide the true state of affairs from investors. He has since pleaded guilty and accepted a 10-year prison sentence.
The question now is how much Mr Lay knew about the false accounting.
Mr Lay has always claimed he was not aware of the accounting tricks used to disguise Enron's true position.
However, it has previously been widely reported that he was warned about them by middle-managers.
In the aftermath of Enron's collapse, Mr Lay refused to testify before various committees and inquiries on Capitol Hill and has previously limited his comments about the Enron affair to expressing his "profound sadness".
He finally gave an interview last month to the New York Times, in which he accepted that as chairman of the company, he must ultimately be held accountable for what happened.
Enron started out as a simple energy producer, but moved on to become an energy trader selling electricity, gas and water at set prices over the long term.
It is said that it gambled badly on future prices, building up millions of dollars in debt that it tried to hide from its balance books.
source: BBC
