A Mexican court has ordered the recapture of a convicted drug lord sentenced to 40 years for the killing of a U.S. Drug Enforcement Administration agent.

Rafael Caro Quintero had been imprisoned for the 1985 kidnapping, torture and murder of DEA agent Enrique "Kiki" Camarena. He walked free thanks to a court ruling in August 2013 after serving 28 years and has not been seen in public since.

Caro Quintero's release infuriated U.S. authorities who offered $5 million for information leading to his capture and trial in the United States.

Acting under a Mexican Supreme Court order to reconsider the release, a court ruled Friday to reverse the earlier decision and ordered Caro Quintero's arrest. But his whereabouts are unknown.