Mired in the restatement process,

Sonus Networks

(SONSE)

said Tuesday that it received a formal order of private investigation from the

Securities and Exchange Commission

.

The maker of communications networking gear also said that a

Nasdaq

panel extended the company's deadline for filing recent financials. The company says it now has until July 19 to file its amended form 10-K/A for the fiscal year ended Dec. 31 and its form 10-Q for the quarter ended March 31, 2004.

The Chelmsford, Mass., telecom switch maker ran afoul of investors in February after revealing that it found problems with its revenue-recognition procedures going back to late 2001. The company fired several managers for unethical behavior and has been working on an accounting review to clean up the books.

The company said that it told the SEC in February of its internal probe and that the agency has been probing Sonus informally since then. Sonus said it has been fully cooperating and will continue to cooperate in this formal investigation.

On Tuesday, Sonus shares fell 39 cents, or 8.6%, to $4.17. Prior to the accounting scandal, Sonus shares traded for around $6.69 a share.