By Jessica Holzer

Of Dow Jones NEWSWIRES

WASHINGTON -(Dow Jones)- The Federal Bureau of Investigation's chief confirmed his organization has opened a probe into J.P. Morgan Chase and Co.'s (JPM) $2-billion-plus trading loss.

"All I can say is we've opened a preliminary investigation and, as you would well know having been in this business for a long time, it depends on a number of factors," FBI Director Robert Mueller said at a Senate Judiciary Committee hearing Wednesday.

Mueller said violations of the federal criminal code or federal securities laws "would be the focus of any ongoing investigation," in response to a question from Sen. Richard Blumenthal (D., Conn.). He said he was hesitant to give anymore specifics.

J.P. Morgan disclosed the huge trading blunder last week. The loss, which stemmed from a complicated trade in the bank's Chief Investment Office, has aroused intense scrutiny in Washington.

The Wall Street Journal reported Tuesday that the Justice Department has opened a probe into the bank's trading loss that is being led by the FBI's New York field office, citing an official who has been briefed on the matter.

Last week, the Securities and Exchange Commission began its own review of the trading loss, examining the company's accounting and disclosures to investors, according to another person familiar with the matter.

-By Jessica Holzer; 202-862-9228; jessica.holzer@dowjones.com