A drug informant who helped the U.S. Drug Enforcement Administration build some of its biggest cases has been arrested and charged with scheming to extort major cocaine traffickers facing extradition from Colombia and the Dominican Republic.

A federal jury convicted two longtime U.S. Drug Enforcement Administration supervisors Wednesday of leaking confidential information to defense attorneys as part of a bribery conspiracy that prosecutors said imperiled high-profile cases and the lives of overseas drug informants.