“There was a time when Guzman Loera was as powerful, or had the influence, that the president had at that time,” said Lopez Obrador. “That made it hard to punish those who had committed crimes. That is now history.”

Last month, Genaro Garcia Luna, a former Mexican government official responsible for public security, was charged in the United States with accepting millions of dollars in bribes from the Sinaloa drug cartel once run by Guzman.

Lopez Obrador has said Mexico will not investigate former President Felipe Calderon, who led the country at the time. But he added the Mexican government would cooperate with U.S. authorities in the probe of Garcia Luna, who moved to the United States in 2012.