FBI chief Robert Mueller confirmed Wednesday that his agency had opened a "preliminary" probe into JPMorgan Chase's multibillion-dollar trading loss.
"All I can say is that we have opened a preliminary investigation" of JPMorgan, Mueller said at a congressional hearing.
The nation's biggest bank disclosed last Thursday that it had lost $2 billion in complex derivatives trading recently, and another $1 billion in related losses was expected by the end of June.
The duration of the FBI investigation "will depend on a number of factors," Mueller said in response to a senator's question.
The director of the US Federal Bureau of Investigation was testifying before the Senate Judiciary Committee in a hearing on FBI oversight.
His testimony confirmed information received Tuesday by AFP from a person familiar with the matter.
Mueller did not comment on the legal issues under scrutiny in the storied Wall Street bank's $2 billion-plus blunder that has rocked financial circles and sparked calls for tighter banking regulation.
Last week, the Securities and Exchange Commission began its own review of the matter, The Wall Street Journal reported Tuesday, citing a person familiar with the matter.
On Tuesday, JPMorgan's embattled leader, Jamie Dimon, faced criticism at the company's annual shareholders meeting over the shock loss, but won their approval to keep his dual position as chairman and chief executive, and his pay package.