CIUDAD JUAREZ, Mexico --At least 13 young people were shot dead and 15 wounded in an attack on a house party in Ciudad Juarez, the second such massacre in less than a week in the violent border city. Gunmen in three cars drove up to the home around 11 p.m. Friday and began shooting, Chihuahua state prosecutors spokesman Fidel Banuelos said Saturday. The dead were aged 14 to 20, Banuelos said, and a 9-year-old child was also gravely wounded. Police found 70 bullet casings from assault weapons typically used by drug gangs. The attackers escaped, and there have been no arrests. Last Sunday, gunmen stormed two homes in Ciudad Juarez, killing seven at a party and two more in another house nearby. Police have not named any suspects or given a possible motive in that massacre. The city across the border from El Paso, Texas, has become one of the world's deadliest amid a turf war between the Sinaloa and Juarez drug cartels. More than 2,000 people have been killed in Ciudad Juarez this year.