Ciudad Juarez, Mexico ? Gunmen stormed two neighboring homes and massacred 13 young people at a birthday party in the latest large-scale attack in this violent border city, even as a new government strategy seeks to restore order with social programs and massive police deployments.

Attackers in two vehicles pulled up to the houses in a lower-middle-class Ciudad Juarez neighborhood late Friday and opened fire on about four dozen partygoers gathered for a 15-year-old boy’s birthday party.

The dead identified so far were 13 to 32 years old, including six women and girls, Chihuahua state Attorney General Carlos Salas told reporters at a news conference at the crime scene. The majority of the victims were high school students, a survivor said.

Salas said a total of 20 people were wounded, including a 9-year-old boy. Authorities earlier gave lower numbers for the wounded because some victims were taken by relatives to hospitals throughout the city and were not immediately located.

Residents of Ciudad Juarez, one of the world’s deadliest cities, no longer go out much to celebrate because of a violent turf war between the Sinaloa and Juarez cartels, who frequently attack their rivals in bars, restaurants, drug rehab centers and other public places.

Salas said the attackers escaped, and police said had no immediate information on any suspects or possible motive. Salas expressed outrage at the situation.