WASHINGTON – FBI Director Robert Mueller said Wednesday that the bureau has launched a preliminary investigation of JPMorgan Chase & Co. after a $2 billion trading loss at the bank.

Mueller’s comment at a Senate Judiciary Committee hearing was the first on-the-record confirmation of the probe. On Tuesday, a law enforcement official said the FBI’s New York office is heading an inquiry into the JPMorgan loss.

“All I can say is we’ve opened up a preliminary investigation,” Mueller told the Senate panel. He said a decision to open a preliminary investigation “depends on a number of factors,” which he did not enumerate.

JPMorgan announced last week that it lost the money in a trading group designed to manage the risks that it takes with its own money. CEO Jamie Dimon said the bank’s strategy was “egregious” and poorly monitored.

The disclosure, a surprise to stock analysts, quickly revived debate about whether banks can be trusted to handle risk on their own in the age of “too big to fail.”

The Securities and Exchange Commission is also looking into the bank’s loss.