The White House replaced the head of the Bureau of Alcohol, Tobacco, Firearms and Explosives and the U.S. Attorney for Arizona on Tuesday in the latest casualties over a botched gun-running investigation known as Operation Fast and Furious.

Kenneth Melson, who led the ATF since April 2009, resigned to take the lesser post of senior advisor to the Assistant Attorney General for the Office of Legal Policy. U.S. Attorney for the District of Minnesota B. Todd Jones was appointed to serve as the ATF's acting director.

Dennis Burke resigned as U.S. Attorney for Arizona, a post in which he advised Melson and his staff on Operation Fast and Furious, which was launched in the fall of 2009.

The operation aimed to bust gun-running that put weapons in the hands of Mexican drug cartels. Fast and Furious was designed to track straw gun buyers until the weapons reached major traffickers along the Mexican border. However those major traffickers were never caught and 2,000 weapons were unaccounted for. Thousands of weapons ended up in the hands of Mexican drug cartels.

Worse, two weapons tied to Fast and Furious were found at the scene of a gunfight near Rio Rico, Ariz., that left Border Patrol Agent Brian Terry dead.

Congressional outcries, mostly from Rep. Darrell Issa, R-Calif., and Sen. Charles Grassley, R-Iowa, have since dogged the operation -- and may yet continue.

While the reckless disregard for safety that took place in Operation Fast and Furious certainly merits changes within the Department of Justice, the Oversight and Government Reform Committee will continue its investigation to ensure that blame isn't off-loaded on just a few individuals for a matter that involved much higher levels of the Justice Department, Issa, chairman of the House panel, told Fox News. 

There are still many questions to be answered about what happened in Operation Fast and Furious and who else bears responsibility, but these changes are warranted. ... I also remain very concerned by Acting Director Melson's statement that the Department of Justice is managing its response in a manner intended to protect its political appointees, Issa said.

Melson and Burke are only the latest casualties of Fast and Furious. Two former top ATF officials in Phoenix, William Newell and William McMahon, were transfered to Washington and last week an assistant U.S. attorney in Phoenix, Emory Hurley, was transferred from the office's criminal division to its civil division.