U.S. Drug Enforcement Administration agents laundered millions in cash for a powerful Mexican drug trafficker and his Colombian cocaine supplier, according to documents made public Monday.

With the help of Mexican federal police officers, the DEA agents and their Colombian informant conducted at least 15 wire transfers to banks in the United States, Canada and China and smuggled about $2.5 million in the United States.

The efforts aimed to infiltrate the Mexican Beltran Leyva drug cartel and a cell of money launderers for Colombia’s Valle del Norte cartel in Mexico and included flying at least one shipment of cocaine from Ecuador to Madrid through a Dallas airport on behalf of the cartels.

Money laundering is a favored tactic of the DEA. The illicit activity – specifically sanctioned as Attorney General Exempt Operations – often violates Mexican sovereignty, facilitates additional criminal activity on the part of the drug cartels, and may be counterproductive, especially in the shadow of the failed gun-running operation Fast and Furious.