Gunmen in Mexico Kill 16 in Attack on a Teenagers’ Party

Thirteen of the victims died at the scene, officials said Sunday, and three more have died since of their injuries.

Chihuahua State authorities gave no motive for the mass killing, but it bore all the signs of the drug violence that has consumed the city over the past three years. Juárez has become ground zero in the government’s war against drug traffickers, as rival cartels use their enormous firepower to fight over drug distribution and routes across the border to Texas.

Although the government argues that the overwhelming majority of murders stem from turf battles among traffickers, there was no immediate evidence to suggest that the slain students were involved with gangs.

Mayor Jose Reyes Ferriz said Monday that investigators had no motive for the crime and that the victims were “innocent civilians.”

Neighbors told El Diario de Juárez, a newspaper, that the students had gathered to celebrate a birthday when just before midnight on Saturday, seven S.U.V.’s drove up and masked gunmen stormed the party.