CHICAGO, Dec. 3  -- U. S. Attorney Patrick Fitzgerald says the undercover probe into police corruption in the Chicago area is "ongoing" and could result in others being charged.

So far the FBI sting has resulted in charges against 15 law enforcement officers for providing what they thought was protection for a dozen large-scale shipments of cocaine and heroin, the Chicago Tribune reported Wednesday.

Thirteen of the officers have been freed without bail. Two others are serving with the Illinois National Guard in Afghanistan, Fitzgerald said.