After years of rampant abuses by undercover Bal Harbour police, the U.S. Justice Department is investigating the millions taken in by the officers who turned a money-laundering sting into a major cash enterprise, spending lavishly on travel and luxury hotels without making a single arrest.

The U.S. Attorney’s Office in Chicago and the Internal Revenue Service carted away hundreds of confidential files last week of the Tri-County Task Force, including records that show the officers regularly withdrew large amounts of cash from the bank with no receipts to show where it went, according to people familiar with the investigation.