Aug. 21--A federal court froze the assets of Rancho Bernardo businessman Mohit A. Khanna after federal regulators said the man defrauded investors of as much as $70 million.

Khanna, 32, allegedly told investors that their money was being put into registered and insured investments with guaranteed annual returns of up to 55 percent and had them sign agreements not to discuss certain aspects of the investments, according to documents filed Monday by the U.S. Securities and Exchange Commission.

But the SEC said that the investments were neither registered nor insured, some investors never received the promised returns, and the remaining investors stopped receiving payments early this year.

U.S. District Judge Robert Benitez on Tuesday ordered the freezing of assets held by Khanna and MAK 1 Enterprises Group LLC, a company that he controls. Benitez also ordered Khanna's passport confiscated and appointed a receiver to oversee MAK 1's assets.

The temporary order, which Khanna hasn't had the opportunity to challenge, remains in effect until a hearing scheduled for Aug. 31.

Khanna didn't respond to telephone messages left Thursday morning at MAK 1's Rancho Bernardo office or to an e-mail sent Thursday afternoon to him at the firm. His attorney, Gustav Bujkovsky of Escondido, didn't respond by press time to a voicemail message Thursday afternoon.

The civil charges brought by the SEC could result in fines and repayment of any ill-gotten gains, but they don't carry the risk of jail time or other criminal penalties.

The agency estimated the size of the alleged fraud at $5 million to $70 million. Lawsuits filed by some of the investors seek a total of about $20 million in damages, according to the SEC.

The alleged fraud began in 2003, was still ongoing last month, and has involved investors in Encinitas, Fallbrook, San Diego, New York, Texas and elsewhere. Khanna allegedly recruited investors through word of mouth and through a Web site.

A San Marcos resident, for example, said in a court filing that he handed over $50,000 to MAK 1 in May 2008 and saw his investment purportedly grow to $77,000. But he tried to withdraw his money earlier this year and has received only $6,000 of it, according to his filing.

Khanna stands accused of various misrepresentations about the amount of money he was managing. SEC investigators say that at one point, Khanna told investors he controlled $519 million.