MILWAUKEE — The U.S. Department of Justice's inspector general has promised to look into a flawed ATF sting in Milwaukee as part of a larger review into how the agency's employees handle certain sensitive cases.

Inspector General Michael Horowitz said he's concerned about how the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives is being run. He wrote to two Republican Congressmen recently saying the Milwaukee sting appeared to raise serious issues relating to the ATF's overall management and oversight, the Milwaukee Journal Sentinel reported.

The Milwaukee sting involved agents setting up a fake storefront to nab criminals selling guns and drugs. But agents lost a machine gun and other weapons, they left behind sensitive documents and their store was burglarized. The agents also refused to pay their rent and warned the landlord against pursuing the matter.

Horowitz's letter on the Milwaukee operation said the ATF's internal report on the incident addressed the management issues that concerned him. But he said his office would still examine the Milwaukee sting, called "Operation Fearless," along with other recent ATF operations.

He didn't say when the review would be completed.

His letter, which was sent to Republican U.S. Reps. Jim Sensenbrenner, of Wisconsin, and Bob Goodlatte, of Virginia, was obtained Monday by the Journal Sentinel. Both congressmen have demanded that ATF release its internal report on the Milwaukee operation, but the agency has refused to comply.

ATF has already come under fire for its handling of "Operation Fast and Furious," a botched arms-trafficking probe in which agents hoped to dismantle gun rings by encouraging the sale of more than 2,000 firearms to gun traffickers. But efforts to track the guns were largely unsuccessful. Hundreds of weapons wound up at crime scenes in the U.S. and Mexico, and two were found at the site of the slaying of a U.S. border agent.

The agency has promised reforms in the wake of Fast and Furious. Horowitz's letter said he would determine if the Justice Department and the ATF responded appropriately to the inspector general's recommendations after that operation.

Before the mistake-ridden gun-buying sting in Milwaukee, ATF agents ran a cigarette-selling sting on the city's south side. Thieves made off from that with two cases of cigarettes worth nearly $10,000.