U.S. authorities have named a new chief for the Bureau of Alcohol, Tobacco, Firearms and Explosives following investigations into the agency's flawed operation aimed at tracking guns flowing to Mexican drug cartels.

The Justice Department announced the changes Tuesday, saying B. Todd Jones, a federal prosecutor in the northern state of Minnesota, is replacing Kenneth Melson as acting ATF director.

The statement says Melson will now become a senior adviser on forensic science in the Justice Department's Office of Legal Policy.

U.S. officials also say Dennis Burke, the U.S. attorney for Arizona, is resigning in the wake of the scandal.

A congressional report said the program, known as “Operation Fast and Furious,” was a “risky new strategy” that allowed hundreds of guns to end up in the hands of violent criminals.

ATF agents told lawmakers that they were ordered by superiors to stand aside while gun buyers purchased weapons that would go to Mexican cartels. They said they were told not to arrest the buyers, but instead track where the purchasers went. The report said ATF would only see the weapons again after they turned up at a crime scene.

The revelations sparked outrage among members of Congress. Two of the weapons under the program's surveillance were found at the scene of a shootout in Arizona where a U.S. border patrol agent was killed.

Mexico has been increasingly critical of U.S. efforts to stop guns from crossing the border.