MEXICO CITY — Federal authorities said Saturday they will take over the investigation into the massacre of 72 migrants at a ranch in northern Mexico because evidence suggests drug traffickers were responsible.
They also said an Ecuadorean migrant who was the lone survivor has refused Mexico's offer of a humanitarian visa and will return to his native country.
Government security spokesman Alejandro Poire said drug cartel involvement would make the killings a federal crime.
The government "will continue its frontal assault against these organizations so that terrible events like those that occurred this week will not be repeated," Poire said. One suspect, who claimed to be 16, was captured at the scene of the massacre and is in custody. Three other suspects and a marine were killed during a raid on the ranch.
Federal authorities said they will wait for survivor Luis Freddy Lala Pomavilla to recover from a gunshot wound in the neck and then help him leave Mexico.
Lala, who is under heavy guard, told investigators Monday that about 10 men who identified themselves as members of the Zetas drug gang traveling in five vehicles intercepted the migrants on a highway in Tamaulipas, a Gulf coast state bordering Texas.
They tied up the migrants, took them to the ranch and demanded they work for the gang, Lala told investigators. When most refused, they were blindfolded, ordered to lie down and shot.
Immigration Commissioner Cecilia Romero said Friday that Lala had been offered a humanitarian visa to stay in Mexico, but his mother said the 18-year-old begged her to arrange for him to come to the United States, where she lives. The AP is not using the woman's name or her location to avoid putting her in potential danger.
The mother said she has been in contact with the Ecuadorean consulate, but officials there said they could only help him return to Ecuador.
Investigators have so far identified 31 of the dead: 14 Hondurans, 12 Salvadorans, four Guatemalans and a Brazilian.
They were the only ones carrying identifying documents, said Honduran Deputy Foreign Minister Alden Rivera. Investigators are collecting DNA from the rest, but Rivera said it might be impossible to identify many more.
In Honduras, worried relatives visited the Foreign Ministry seeking news on relatives believed to be in Mexico.
Maria Cruz was looking for word about her son, Denis Moreno, 34, who last contacted her from a city along the U.S.-Mexico border.
"I hope he is not on the list," she told a Honduran television station, sobbing. "I hope not."
Gangs have long kidnapped migrants and demanded payment to cross their territory. But the Mexican government says the cartels are increasingly trying to force vulnerable migrants into drug trafficking, a concern also expressed by U.S. politicians demanding more security at the border.