Mexican security officials say one of the founders of the Zetas drug cartel has been killed in a gun battle in the north-eastern state of Tamaulipas.
Galindo Mellado Cruz is accused of being one of the original members of the Zetas, which first emerged as a group of enforcers for the Gulf cartel.
The two groups later split and became bitter rivals, their fights accounting for much of the violence in the area.
He is believed to be among five gunmen shot dead by the army on Friday.
A Tamaulipas state official told the Associated Press news agency that while Mellado no longer held a command position within the Zetas, he had been one of the 30 ex-special forces members to found the group.
Analysts say the Zetas now control more territory than any other criminal gang in Mexico.
They are infamous for their extremely violent methods, routinely decapitating rivals and hanging their bodies from bridges.
The war between the Zetas and their former paymasters, the Gulf cartel, has turned Tamaulipas into one of Mexico's most violent states.
Mellado was on the run after escaping from prison where he had been jailed after being accused of armed robbery, rape and murder, the official said.
He was killed in a raid on his hideout in the city of Reynosa along with four other armed men. One soldier also died in the fire fight.
It is not clear how the security forces tracked him down.
The security forces have recently landed a series of heavy blows against Mexico's drug cartels.
Earlier this year, they arrested the world's most wanted drug lord, Joaquin "Shorty" Guzman. And last year they detained the leader of the Zetas, Miguel Angel Trevino.
But a number of high-ranking security officials have also been killed, including the Tamaulipas state intelligence chief, who was shot dead along with his bodyguards in Reynosa last week.