US regulators have filed civil charges against four former executives at telecom-equipment firm Nortel Networks.
A number of top firms have been caught up in accounting problems
The Securities and Exchange Commission accused the executives of accounting fraud that boosted earnings between September 2000 and January 2004.
Among the accused are former chief executive Frank Dunn and ex-financial officer Douglas Beatty.
Nortel said it was unable to comment on the proceedings, but would cooperate with the SEC investigation.
Former-controller Michael Gollogly and ex-assistant controller MaryAnne Pahapill were the other Nortel executives charged by the SEC.
Should the charges be proved then the watchdog wants the four to be fined, barred from working as officers or directors of a public company, and have to repay any proven ill-gotten gains.
"The fraudulent conduct at issue here was egregious and long-running," the SEC said.
"Each of the defendants betrayed Nortel's investors and their misconduct gave rise to billions of dollars in shareholder losses," said Linda Thomsen, the SEC's enforcement director.
Since 2003, Nortel has had to restate its results each year as problems have come to light.