( CNN ) -- Federal agents ca n't account for more than 1,400 guns after a widely criticized operation aimed at tracing the flow of weapons to Mexican drug gangs , sources with knowledge of the investigation tell CNN . Of 2,020 guns involved in the Bureau of Alcohol , Tobacco , Firearms , and Explosives probe dubbed `` Operation Fast and Furious , '' 363 have been recovered in the United States and 227 have been recovered in Mexico . That leaves 1,430 guns unaccounted for , the sources said . The ATF operation was intended to build cases against Mexican drug cartels by allowing firearms to go from the United States into Mexico . The hope was by tracing the guns in Mexico , agents would be able to determine the structure of various cartels and then bring them down . The problem was that once the guns were allowed to `` walk , '' there was no way to recover them until they turned up at crime scenes . The operation has been widely criticized in Congress , with the chairman of a House committee that investigated the issue calling it `` felony stupid . '' Rene Jaquez , the ATF 's former attache in Mexico City , told CNN the operation never should have happened . `` Guns traditionally are just not allowed to leave the undercover operation for fear that it will enter into the criminal element and then be subsequently used in a crime at a later date , '' Jaquez said . `` And the last thing any one of us as law enforcement officers wants to have attributed to us is the death of an innocent individual by a gun that was lost during one of our operations . '' But the ATF knowingly allowed individuals to purchase weapons that they knew would end up in the hands of criminals on both sides of the border . And when Border Patrol Agent Brian Terry was killed in Arizona in December , two AK-47 variants that were allowed to `` walk '' under the program were found at the scene . In Mexico , the operation drew sharp criticism from top officials , who have long said that U.S. weapons are fueling the country 's bloody drug war . And ATF agents in Arizona told the House Oversight and Government Reform Committee in June that they cringed every time they heard of a shooting after the program had been under way for some time . Over the past several months , questions have arisen regarding who in government knew about and sanctioned this operation . Even though the operation was run out of the ATF 's field office in Phoenix , Jaquez said it is highly unlikely that officials at the Department of Justice in Washington were not informed . `` You have to understand , this program was in operation 18 months or more before we had any idea it existed , '' said Sen. Charles Grassley , R-Iowa . `` And as I look back on it now , it was a , it 's a big joke '' -- one Grassley says is n't so funny since the guns have turned up in the hands of criminals . In late June , President Barack Obama said `` appropriate action '' would be taken once an investigation of the program is completed . But so far , details about who knew what and when have been scarce . Last week , the embattled acting director of the ATF , Kenneth Melson , was interviewed by congressional investigators in a closed session . While the content of the interview remains confidential , Melson 's personal attorney was at his side . Grassley has stated he plans on seeing this investigation to its conclusion . `` There 's a basic principle of government here that the people in the Justice Department are forgetting -- the public 's business should be public , '' he said .
`` Operation Fast and Furious '' involved more than 2,000 guns , sources tell CNN . Fewer than 600 have been recovered in the United States and Mexico , they say . The operation has been sharply criticized by members of Congress .