CBS News and the nonprofit Center for Public Integrity reported that agents of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives investigating gunrunning by cartels allowed hundreds of guns purchased in the U.S. to go into Mexico.

"Carrying out this type of operation in our country is unacceptable. It violates trust and also undermines national sovereignty," said Sen. Luis Alberto Villarreal, a member of President Felipe Calderon's National Action Party.