Nortel Networks has said the US Securities and Exchange Commission has launched a formal investigation into the company's restatement of its financial results.
The SEC had been been conducting an informal inquiry into the restatements, and the Nortel Networks Audit Committee had also conducted an independent review, Nortel said.
"Nortel Networks has been fully cooperating with the SEC and will continue to do so in order to bring the inquiry to a conclusion as promptly as possible," the company said.
Last month, Nortel announced that it would probably restate its results for the second time in six months and that it would delay filing its annual 2003 financial statements with the SEC.
In March, the company also said it placed its chief financial officer and controller on paid leave pending the completion of the independent review being conducted by the audit committee.