MEXICO CITY -- Mexican drug boss Hector Manuel Beltran Leyva, once one of Mexico's most-wanted men, died Sunday after suffering a heart attack in jail. The Interior Ministry said that Beltran Leyva, 56, was transported to a hospital the central city of Toluca after complaining of chest pains but that doctors were unable to save him.

Beltran Leyva received the necessary medical attention and prison and hospital personnel did everything in their capacity to revive him, the ministry said, emphasizing that security protocols were observed.

Beltran Leyva was arrested in 2014 in San Miguel de Allende, a colonial city favored by U.S. retirees, but had eluded an extradition request from the United States.

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The family-run Beltran Leyva cartel was once a leading player in Mexican drug trafficking, with control of the U.S. border region in Sonora. In 2008, a federation dominated by the Sinaloa Cartel, which included the Beltran Leyva organization, broke apart, sparking one of the bloodiest episodes of Mexican cartel infighting.

Brothers Alfredo and Carlos were arrested, while Arturo was killed by security forces. Hector's wife Clara Laborin Archuleta was arrested in 2016 after taking over cartel operations and trying to reassert control in the Pacific Coast resort of Acapulco. Splinter groups have subjected Acapulco to unrelenting waves of violence and extortions.

Sinaloa Cartel leader and infamous escape artist Joaquin "El Chapo" Guzman, who is currently on trial at a federal court in Brooklyn, is suspected of having provided intelligence that led to the arrest of Alfredo.