MEXICO CITY -- A Mexican prosecutor said there are indications that an old-guard drug lord mistakenly released from prison in 2013 is apparently trying to get back into the drug trade.

Jorge Gonzalez, the attorney general of the northern state of Chihuahua, told reporters Tuesday there is evidence that Rafael Caro Quintero may be trying to muscle in on the Sinaloa cartel's operations. The area on the border of Sinaloa and Chihuahua states has seen an upsurge in violence in recent weeks.

Caro Quintero, 63, was a founding member of one of Mexico's earliest and biggest drug gangs, the Guadalajara cartel. He helped establish a powerful cartel based in the northwestern Mexican state of Sinaloa that later split into some of Mexico's largest drug organizations, including the Sinaloa and Juarez cartels.

"At the national level the possibility has been recognized that one of the country's best-known drug traffickers, Rafael Caro Quintero, may be invading Chihuahua, and we have information that he is planning to come here," Gonzalez told reporters. "We are taking care and protecting against a possible advance by this man who could want to come here and fight the Sinaloa cartel for part of the criminal work they carry out."

Joaquin "El Chapo" Guzman and other associates ran the Sinaloa cartel for decades after Caro Quintero was imprisoned in the 1980s. But Guzman's re-capture in January may have encouraged other traffickers to retake parts of his territory.

Caro Quintero walked free in 2013 after a federal court overturned his 40-year sentence in agent Enrique "Kiki" Camarena's kidnapping, torture and murder. The three-judge appeals court in the western state of Jalisco ordered Caro Quintero's immediate release on procedural grounds after 28 years behind bars, saying he should have originally been prosecuted in state instead of federal court.

Mexico's Supreme Court later annulled the order, saying Camarena was a registered U.S. government agent and therefore his killing was a federal crime. An arrest warrant was issued for Caro Quintero, who has not been seen since his release.

Mike Vigil, a former chief of international operations for the U.S. Drug Enforcement Administration, said the Mexican military has information that Caro Quintero has aligned himself with members of what remains of the Beltran Leyva drug trafficking group to try to wrest control of Ciudad Juarez and the surrounding state of Chihuahua from the Sinaloa cartel.

Vigil said Mexican authorities have intercepted phone calls in which callers have described the new fight for control of the profitable drug trafficking routes. Mexican authorities attribute a recent spike in killings in the area is being attributed to the fight, Vigil said.