Dell told government regulators on Monday that it cannot file a financial statement for its 401(k) plan, as the company continues to struggle with investigations of its accounting practices.

Dell has missed the deadlines for filing its past three quarterly earnings reports, called Form 10-Qs, and its annual report, Form 10-K. That has earned it a series of warnings that the Nasdaq stock exchange may stop trading Dell securities.

The company's trouble started last year when the US Securities and Exchange Commission (SEC) began an investigation into Dell's accounting practices. The US Attorney for the Southern District of New York has launched a similar effort. To comply with investigators' demands, Dell initiated an internal audit, which has already found evidence of misconduct and accounting errors.

As long as those investigations continue, Dell says its earnings reports will be only preliminary, not officially audited. The company has not yet decided whether it will have to restate past figures, but said in June it was nearing the end of its internal inspection.

In the meantime, the company's results continue to sour, as Dell falls farther behind rival HP in market share. In an effort to recapture profit, Dell announced extensive layoffs in May, cutting 10% of its 88,100 jobs.

The latest form Dell missed is for a financial statement called Form 11-k, describing the status of the 401(k) retirement savings plan for Dell and for Dell Financial Services. The company declined to file it because of the ongoing investigation, the same reason it gave for missed deadlines to file recent quarterly earnings reports, said Dell spokesman Bob Pearson.

Dell missed the deadline "due to the questions raised in connection with the independent investigation being conducted by the Audit Committee of the company's Board of Directors," the company said in an SEC filing submitted Monday.

"Management is committed to resolving the issues raised in connection with the investigation, and is working diligently to file the delayed reports as soon as possible," Dell said.