CIUDAD JUAREZ, Mexico (AP) - Gunmen burst into a drug treatment center in the northern Mexican border city of Ciudad Juarez and shot to death 10 people, the second such mass killing this month.
Investigators said the attack was part of a turf battle between the Juarez and Sinaloa cartels in the city, which has seen the worst of Mexico's drug gang violence.
Gangs use some drug treatment centers to hide their members from rivals, Chihuahua state Attorney General Patricia Rodriguez said. She did not name suspects or say which cartel may have been behind the massacre.
Police say nine men and one woman were killed in the attack just before midnight Tuesday at the Anexo de Vida center in Mexico's most violent city. Two people were seriously wounded.
Most of the victims are believed to have been recovering addicts staying at the facility.
"Why? Why them?" said Pilar Macias, weeping after she identified the body of her brother, Juan Carlos Macias, 39. "He was recovering, he wanted to get back on the right track and they didn't let him, they didn't give him a chance."
"This is going to kill my mother," Macias said. "She's very sick and this is going to kill her."
Macias said the mother had encouraged her son to enter the facility for treatment of his cocaine addiction three months ago.
Maria Hernandez also had come to the state prosecutor's office to identify the body of her 25-year son.
"He was good, he didn't hang out with gangs, he didn't have 'narco' friends," she said. "He just began with marijuana, and then ... they killed him."
Pools of dry blood and bloodied footprints were visible Wednesday in the courtyard of the drug and alcohol rehab center where the shooting occurred.
The center is located in a poor neighborhood with dirt streets, some of which were impassable due to recent rains.
Regional Deputy Attorney General Alejandro Pariente said records showed the center had not been registered with the government and may have been operating clandestinely. He said 10 other centers in Ciudad Juarez have been closed for operating illegally.
On Sept. 2, gunmen lined patients against a wall at another rehabilitation center in Ciudad Juarez and then riddled them with bullets, killing 18.
Five men were killed at another rehabilitation center in June, and in August 2008, gunmen barged into a pastor's sermon at a rehabilitation center and opened fire, killing eight people. Authorities have not said if any of the attacks are related.
The Juarez cartel, named after its historic base in the border state of Chihuahua, is locked in a bloody battle with the Sinaloa cartel, another long-established gang, for lucrative drug routes into the United States.
Ciudad Juarez is Mexico's most violent city, with more than 1,300 killings this year. The bloodshed has continued despite a buildup in troops since March.
Early Wednesday, gunmen burst into a bar in Ciudad Juarez and shot to death five men, police said. They said they knew of no motive for the attack. Hours later, a federal investigator and a civilian were shot dead in front of the state attorney general's offices in Ciudad Juarez.
Surging gang violence has claimed 13,500 lives since President Felipe Calderon took office in 2006 and deployed extra soldiers across the country to fight cartels.
Also Wednesday, navy personnel arrested of a suspect in the June 1 kidnapping of Francisco Serrano, the customs administrator for the Gulf coast state of Veracruz, who remains missing.
Jose Osiris was captured in the port of Veracruz along with 10 other people who may have been accomplices, Navy spokesman Jose Luis Vergara said at a news conference in which the suspects were presented to the media.
Authorities, who did not take questions at the news conference, did not say what evidence there was against Osiris or if his capture might shed light on Serrano's fate. Ricardo Najera, a spokesman for the attorney general's office, said Serrano's whereabouts remain unknown.
Serrano had recently launched a new system to check shipping containers at Veracruz, one of Mexico's most important ports and the scene of increasing drug violence.
In the southern state of Guerrero, meanwhile, police reported they had found the decomposed bodies of four men by the side of a highway. Because of their poor condition, the cause of death and identity of the bodies has not yet been established.