The scale of accounting errors at the bankrupt telecommunications firm WorldCom is almost double the level previously reported.
WorldCom said that an internal audit had discovered that $3.3bn in earnings was improperly recorded on its books from 1999 to the first quarter of this year.
This is on top of the $3.85bn in expenses the company previously said that it had improperly booked as long-term capital investments.
As a result of the discovery, WorldCom said that its financial statements for the year 2000 would have to be reissued.
Economists have said that the new announcement could add fuel to the crisis in financial markets, which have dropped significantly in recent months.
The wave of accounting scandals in the US, starting with energy giant Enron last autumn and followed by Global Crossing and Tyco have rocked confidence in corporate America and sent markets tumbling all over the globe.
WorldCom is under investigation by the Securities and Exchange Commission and the US Justice Department and Congress.
The crisis has led to the arrests of its former Chief Financial Officer Scott Sullivan and former Controller David Myers on fraud charges. They could face up to 15 years in jail if convicted.