WASHINGTON — A Mexican drug kingpin convicted in the 1985 killing of a DEA agent was added Thursday to the FBI's list of most-wanted fugitives.

Rafael Caro Quintero was mistakenly released from a Mexican prison in 2013 while serving a 40-year sentence for the kidnapping and murder of DEA Special Agent Enrique Camarena Salazar.

"We believe he is still in Mexico," FBI Deputy Director David Bowdich said at a news conference.

Bowdich said the most-wanted list is "one of our most valuable tools," and that 484 of the 518 fugitives who have been on the list have been captured.

Authorities also increased the reward for Caro Quintero's capture to $20 million. James Walsh, a deputy assistant secretary in the State Department, said the amount is the highest offered by the Narcotics Reward Program and the highest among the 33 active targets.

No Mexican officials attended the news conference, but DEA acting administrator Robert Patterson said, "Our working relation with Mexico at our level is superb."

Also Thursday, federal officials unsealed an additional indictment against Caro Quintero, accusing him of trafficking in methamphetamine, heroin, cocaine and marijuana from 1980 until 2017.

Caro Quintero has controlled the Sinaloa Cartel along with Ismael "El Mayo" Zambada Garcia since the arrest of Joaquin "El Chapo" Guzman.

Authorities say it's the first time that a suspect sought by the DEA has been added to the FBI's list.

While the Mexican government has made little progress in capturing Caro Quintero, or in investigating those responsible for his release, Mexican reporter Anabel Hernandez has interviewed him in the mountains of northern Mexico without revealing the location. Caro Quintero claimed in those interviews that he was no longer involved in the drug trade.

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Associated Press writer Mark Stevenson in Mexico City contributed to this story.