MEXICO CITY – A wounded migrant stumbled into a military checkpoint and led marines to a gruesome scene, what may be the biggest massacre so far in Mexico’s bloody drug war: a room strewn with the bodies of 72 fellow travelers, some piled on top of each other, just 100 miles from their goal, the U.S. border.

The 58 men and 14 women were killed, the migrant told investigators Wednesday, by the Zetas cartel, a group of former Mexican army special forces known to extort migrants who pass through its territory.

If authorities corroborate his story, it would be the most horrifying example yet of the plight of migrants trying to cross a country where drug cartels are increasingly scouting shelters and highways, hoping to extort or even recruit vulnerable immigrants.

“It’s absolutely terrible and it demands the condemnation of all of our society,” said government security spokesman Alejandro Poire.

The Ecuadorean migrant stumbled to the checkpoint on Tuesday, telling the marines he had just escaped from gunmen at a ranch in San Fernando, a town in the northern state of Tamaulipas about 100 miles from Brownsville, Texas.

The Zetas so brutally control some parts of Tamaulipas that even many Mexicans do not dare to travel on the highways in the states.

Many residents in the state tell of loved ones or friends who have disappeared traveling from one town to the next. Many of these kidnappings are never reported for fear that police are in league with the criminals.