From the LA Times:
When the ATF made alleged gun trafficker Manuel Fabian Celis-Acosta its primary target in the ill-fated Fast and Furious investigation, it hoped he would lead the agency to two associates who were Mexican drug cartel members. The ATF even questioned and released him knowing that he was wanted by the Drug Enforcement Administration.
But those two drug lords were secretly serving as informants for the FBI along the Southwest border, newly obtained internal emails show. Had Celis-Acosta simply been held when he was arrested by theBureau of Alcohol, Tobacco, Firearms and Explosives in May 2010, the investigation that led to the loss of hundreds of illegal guns and may have contributed to the death of a Border Patrol agent could have been closed early.
Documents obtained by the Los Angeles Times/Tribune Washington Bureau show that as far back as December 2009 — five months before Celis-Acosta was detained and released at the border in a car carrying 74 live rounds of ammunition — ATF and DEA agents learned by chance that they were separately investigating the same man in the Arizona and Mexico border region.
ATF agents had placed a secret pole camera outside his Phoenix home to track his movements, and separately the DEA was operating a “wire room” to monitor live wiretap intercepts to follow him.