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, AP reported.
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.