The FBI is investigating Peregrine Financial, a Chicago-based futures broker, after a $220m (£141m) shortfall in customer funds was discovered shortly after an apparent suicide attempt by its chairman, Russell Wasendorf.
Regulators at the Commodity Futures Trading Commission also said it had filed a complaint against Peregrine Financial and its owner, alleging fraud and misappropriation of customer funds.
The complaint, filed in the Northern District Court of Illinois, says Peregrine and Mr Wasendorf had violated customer fund segregation laws and made false statements in financial declarations filed with the commission.
On Monday a Peregrine subsidiary, PFGBest, a foreign exchange and commodity futures broker, told customers their accounts had been frozen after an apparent suicide attempt by its chairman. A few hours later, an industry body said about $220m in customer funds were not in the brokerage's bank accounts.
The CFTC is seeking a restraining order to freeze assets, appoint a receiver and preserve records.