Reporting from Mexico City — Gunmen stormed a private drug treatment center in Tijuana and executed at least 13 men at close range, authorities in Baja California said Monday.
The Sunday night attack was the first big assault on a clinic in the border city, where Mexican officials say their crackdown against drug gangs has weakened criminal groups and restored relative calm. Similar attacks have taken place on treatment centers in the northern state of Chihuahua, home to Ciudad Juarez, the country's most violent place.
Two to four attackers gathered the Tijuana victims in a room of the El Camino treatment center and opened fire with assault rifles, authorities said.
It was not immediately clear how the shooters gained access to the site, which sits behind a thick steel gate in a working-class neighborhood in the eastern part of the city. Authorities said they were unsure of the motive. Victims were 19 to 56 years old.
Survivors reported hearing gunfire for about two minutes.
"I was there in back, and as soon as I heard, 'Everyone on the floor! Everyone on the floor!' we thought they were police," a survivor told the Tijuana-based Border News Agency. "I threw myself under the bed and didn't come out."
Melquiadez Hernandez Esparza, 52, identified as the manager on duty at the time, said he stayed in a nearby room with nine clients until the shooting stopped.
The center, one of about 175 drug and alcohol treatment facilities in Tijuana, was reportedly home to about 40 addicts who built doghouses and did other carpentry work to support the facility. Authorities said the center was not licensed.
Elsewhere in Mexico, treatment centers have served as havens for fugitives and outlets for drug sales, making them targets for drug cartels and ordinary street gangs. In June, 19 people were slain in an attack on a clinic in the city of Chihuahua.
Baja California's prosecutor, Rommel Moreno, said Sunday's attack may have been tied to the Mexican army's record-setting seizure last week of 134 tons of marijuana in Tijuana.
Soon after the killings, someone broke into the police frequency, playing narco-ballad music and warning that the attack was "a taste" of Juarez-style carnage, a police official said. Moreno confirmed a news report that the radio voice threatened that a person would die for every ton of marijuana seized.
"It is perverse to me the way they are trying to scare people," Moreno told a Mexico City radio station. "What we are trying to do is provide calm."
Officials said they believe the marijuana stockpile belonged to the drug-trafficking group based in the northwestern state of Sinaloa and led by the country's most-wanted suspect, Joaquin "Chapo" Guzman.
If true, it may signal that the powerful Guzman-led cartel is moving to wrest control of the Tijuana corridor from its longtime rival, the Arellano Felix cartel, weakened by more than two years of infighting.
Security forces have been credited with debilitating the Arellano Felix group, but they could face a greater test from the more powerful Sinaloans. Residents fear that their city could turn into a battleground similar to Ciudad Juarez, where rival cartels have been at war for nearly three years, leaving more than 6,500 dead.
Reprisal killings are common after drug gangs lose big loads of contraband, and Tijuana authorities were braced for violence after last week's seizure, whose estimated value was $200 million.
Even before that haul, a spate of killings marred what Tijuana boosters and many residents were describing as an encouraging period of relative peace. More than two dozen people were slain during the first two weeks of October.
Two years ago, soaring kidnappings and frequent gangland slayings related to an internal cartel feud spurred many residents to flee across the border into San Diego County.
But the most spectacular violence subsided with the arrest early this year of Teodoro Garcia Simental, who led one of the warring factions. Well-to-do residents began to trickle back.
Sunday's attack was the deadliest in the city of 1.5 million since 2008.
Calm has proved deceptive, and short-lived, in other drug hot spots. Still, officials have sought to showcase Tijuana as an emblem of success in the Mexican government's controversial 4-year-old war against drug cartels and the iron-handed approach of the police chief, Julian Leyzaola.
This month, the city threw itself a big two-week party, drawing luminaries such as Al Gore to promote Tijuana's role as a business and innovation hub and try to push the drug issue to the background.