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Activists march down Wall Street holding a cutout of JP Morgan CEO Jamie Dimon, during a protest against budget cuts and bank practices, in New York, May 12, 2011. Now, the FBI is launching a preliminary investigation in the company for possible criminal activity. - 

David Brancaccio: The FBI is investigating possible criminal behavior at JPMorgan Chase after that $2 billion trading loss disclosed by the bank the other day.

Marketplace's Gregory Warner reports.

Gregory Warner: Exactly how a trader at JPMorgan gambled and lost $2 billion is still far from clear. But a key question will be this: was that multi-billion dollar bet a so-called hedge to balance out the risk of other investments? Or was the bank betting shareholder money for its own profit?

The FBI probe is still preliminary. Bill Singer is a partner at Hersokovitz PLC. He says the FBI may not even know yet what if any criminal charges apply.

Bill Singer: You can’t build a criminal case based upon quote unquote public documents. You need informants, you need whistleblowers.

Singer says last night’s anonymous leak about the FBI investigation could be intended to draw out potential whistleblowers at JPMorgan.

Singer: It’s probably sending out a warning flare, that if you want to come in and talk to us, do it now, before we find you.

Meanwhile at the bank’s annual meeting in Tampa yesterday, CEO Jamie Dimon said his company’s mistakes were quote unfortunately self-inflicted.

I’m Gregory Warner for Marketplace.

Follow Gregory Warner at @radiogrego