Richard Causey, the last of the top Enron Corporation executives to learn his punishment, has been jailed for five-and-a-half years for his role in one of the biggest corporate scandals in US history.

Andrew Fastow, the former chief financial officer of Enron Corp, reported to the Houston FBI office where he was to surrender on criminal charges with defrauding shareholders through a secret agreement guaranteeing that Enron shield his LJM partnership from losses.

A top lieutenant to Enron’s former chief financial officer will today plead guilty to criminal charges, sources close to the investigation in the US said.

Former Enron executive Michael Kopper is to plead guilty to wire fraud and money laundering charges, the first admission of guilt in the federal investigation of the fallen energy giant.

Former Enron chief executive Jeffrey Skilling will face questioning before Congress with other Enron officials whose versions of events conflict with his.