A major Mexican drug kingpin was arrested Friday in northwestern Mexico.

Rafael Caro Quintero was taken into custody in the state of Sinaloa by Mexican Marines. Quintero had previously served time for the 1985 kidnapping and murder of U.S. Drug Enforcement Agency officer Enrique “Kiki” Camarena and served nearly three decades in prison in Mexico before being released in 2013.

DEA administrator Anne Milgram claimed her agency had worked with Mexican authorities on the operation leading to the arrest, which she described as the fruit of years of blood, sweat and tears.

But on Monday, Mexican President Andrés Manuel López Obrador disputed that account, saying that the Mexican Marines had carried out the entire investigation leading up to the arrest and the apprehension itself. That echoed a statement over the weekend from U.S. Ambassador to Mexico Ken Salazar.