Computer maker Dell is to delay filing its second-quarter results and has suspended a share repurchase plan as a result of an accounting probe.
The problems with Dell's accounts could date back to 2002
The group said "questions raised" by a Securities and Exchange Commission (SEC) inquiry had delayed the filing.
The SEC probe and an internal inquiry show Dell may have mis-stated its accounts, the firm said.
It added the US Attorney for the Southern District of New York had also now subpoenaed financial documents.
The investigations centre on Dell's accounts dating back to 2002.
"We are fully cooperating with the investigations and working to resolve any and all issues raised in connection with those investigations as quickly as possible, and we will take any appropriate remedial or corrective actions to address any problems," said chairman Michael Dell.
The company added that the investigations showed the problems with its accounts may be linked to issues relating to accruals, reserves and other balance sheet items.
In a statement the world's biggest computer maker said it had not determined what effect the problems would have.
As well as delaying the filing of its results for the three months to 4 August with regulators, Dell also said it had postponed an analyst meeting set for 13 September.
However, it added it planned to file the second-quarter results "as soon as possible".
The probe is the latest problem to hit the computer maker. Recently it was forced to recall more than four million batteries - which were made by Sony - in its notebook computers because of a fire risk.
Shares in the group fell 80 cents, or 3.7%, in pre-market trade to $20.85 on the news.