The United States government officially requested the re-arrest of Rafael Caro Quintero on Wednesday, the drug lord unexpectedly freed from prison last week in Mexico, for the 1985 kidnapping, torture and murder of a Drug Enforcement Administration agent.

It's far from clear that either country will be able to find Quintero, 60, who has not been seen in public since he walked out of prison before dawn Friday after an appeals court overturned his 40-year sentence on procedural grounds. He had been jailed for 28 years.

The Mexican Attorney General's Office said the U.S. asked for Caro Quintero to be held on an unspecified indictment filed in California. Caro Quintero has been charged in two indictments in California, one alleging drug offenses and the other accusing him in the murder of DEA agent Enrique "Kiki" Camarena.

U.S. officials declined to comment on the case, but Mexican officials have said they could not extradite Caro Quintero for the Camarena killing, making it likely he is now being sought on the drug charges.

Caro Quintero remained on the DEA's most-wanted list during his jail term, but Mexican Attorney General Jesus Murillo Karam told reporters Tuesday that there was no U.S. request for his extradition pending at the moment the prisoner was freed.

Caro Quintero walked free after a three-judge federal appeals court in the western state of Jalisco overturned his sentence in Camarena's kidnapping, torture and murder. The panel ordered Caro Quintero's immediate release on procedural grounds, saying he should have been tried in a state court instead of federal court.

Murillo Karam has said the judges should have referred the case to another court instead of freeing Caro Quintero in the middle of the night with no public notification.

U.S. officials say they had no notice of the court decision, and members of Congress have called it a setback to U.S.-Mexican law-enforcement cooperation.

Based on reporting by the Associated Press.

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