The navy said in a statement that in a battle Sunday afternoon in Coahuila state in northern Mexico between marines and men armed with guns and grenades, two men were killed, one bearing “strong signs” of being Heriberto Lazcano, known as El Lazca and the main leader of the Zetas.
The navy said it was conducting forensic tests to positively identify the men, but the prospect of having eliminated one of Mexico’s most wanted criminals led to leaks just before the most-watched evening newscast, which reported the possibility that Mr. Lazcano had been killed.
If confirmed, his death would give President Felipe Calderón probably his biggest victory against drug and organized crime groups, two months before he ends his six-year term with a legacy likely marked by his escalation of the battle against gangs and the brutal violence they have wrought.
In a twist, two Mexican newspapers reported on Tuesday that the corpse that the authorities believed to be Mr. Lazcano was taken away from a funeral home by armed people or family members. They reported that law enforcement authorities had already taken fingerprints, photographs and other material to aid in the identification, but the loss of the body would surely add to doubts and mystery over the man and the case.
The Zetas stand out among the country’s two or three largest criminal groups for their butchery, carrying out beheadings and other mutilations to intimidate enemies and murdering those, including migrants passing through their turf mainly in northeastern Mexico, who do not follow their orders.
They have staged some of the country’s most spectacular jailbreaks — they were said to be behind one last week in which scores of inmates walked out of a state prison — and most brazen attacks on Mexican security forces.
Mr. Lazcano deserted more than a decade ago from an elite Mexican Army unit. Along with other former special forces operatives from Mexico and Guatemala, he founded, trained and recruited armed men to serve as enforcers for the powerful Gulf Cartel.
The Zetas split off on their own two years ago and have fought their former allies and the Sinaloa Cartel, run by the most wanted drug lord, Joaquín Guzmán, known as El Chapo, or Shorty, who is wanted as badly here as Osama bin Laden once was by the United States.
Lately, security analysts have reported that the Zetas themselves are fracturing into at least two groups, and if confirmed, Mr. Lazcano’s death, along with the recent captures of other top Zeta capos, would likely sow even more confusion and violence among the ranks. In the scramble, Zeta leaders are believed to be turning on one another through executions and providing tips to law enforcement. Another Mexican Navy operation against the Zetas on Sunday, in Nuevo Laredo, led to the capture of a man that the authorities said was the gang’s regional leader in three border states.
Eduardo Guerrero, a security consultant who closely tracks organized crime here, said it appeared that the Mexican government, frequently acting on intelligence provided by the United States Drug Enforcement Agency, has been hitting the Zetas particularly hard and capitalizing on the divisions in the group.
He said there had been 17 major arrests of leaders of the group over the past year.
Mr. Lazcano, who is also known by the nickname the Executioner, is wanted by American law enforcement on drug trafficking and related charges, with a $5 million reward on his head.
It was unclear, given Mr. Lazcano’s military service and notoriety, why the Mexican Navy did not have the means to make a positive identification before putting out their statement. Officials did not respond to queries.
The marines are considered Mexico’s most professional force and have made some of the most significant captures and kills in the drug war. But they were also responsible for one of the bigger fiascos in Mr. Calderón’s term, when they falsely arrested a man in June who was presumed to be the son of Mr. Guzmán. Prosecutors later said it was not him.