(Recasts, adds quotes, details from hearing)

By Randall Mikkelsen

WASHINGTON, Feb 11 (Reuters) - The FBI's caseload of fraud investigations into major corporations and banks could climb from 38 into the hundreds as the economic crisis deepens, a bureau official told Congress on Wednesday.

U.S. officials also told a Senate hearing several criminal investigations related to the $700 billion federal bailout program were already in progress.

The comments came as Congress moves to tighten fraud laws and demands that the Justice Department prosecutes financial crimes more aggressively to safeguard public money used in financial bailouts that could reach trillions of dollars.

"I want to see people prosecuted," said Senate Judiciary Committee Chairman Patrick Leahy said. "Frankly, I want to see people go to jail."

The Vermont Democrat has proposed legislation to hire more investigators and tighten laws against financial fraud. Aides said his committee could act within weeks.

Government officials told the hearing they needed more money and other resources to investigate fraud.

The FBI's caseload of 38 corporate fraud and financial-institution investigations linked to the crisis represents an increase from 24 publicly reported last year. But the effort has yielded few major prosecutions.