One of the guns found in El Chapo's hideout has been traced to Operation Fast and Furious.
The drug lord was arrested two weeks ago, months after he escaped from a Mexican prison.
ABC News has learned a rifle found at his hideout was part of the operation in which the ATF allowed gun dealers in Arizona to sell weapons to straw purchasers.
The plan was to trace the weapons into Mexico to find drug cartels, but it is alleged the program failed and lost track of hundreds of guns sent to Mexico.
Gun in 'El Chapo' hideout traced to Operation Fast and Furious