An 800,000-gallon water tank filled to the brim ruptured Friday, drowning two people, injuring 16 and leaving 500 people homeless in a squalid neighborhood across the border from El Paso, Texas, officials said.

Police said authorities do not know what caused the concrete tank to rupture, sending a wall of water cascading into the impoverished neighborhood, triggering panic among the residents.Several people were reported missing, and police continued to search through the rubble Friday evening.

One of the dead was an 8-year-old boy and the other was a 16-year-old youth. Both were residents of Colonia Lopez Mateos, the southwestern Juarez neighborhood immediately below the tanks, police and fire officials said.

Officers said 16 people were taken to area hospitals, some of them seriouly injured, others slightly hurt. Witnesses said a 9-year-old girl who was playing next to the tank was among those seriously injured.

Authorities said at least 50 houses were severely damaged and 10 homes were demolished, leaving 500 people homeless. The houses were mainly adobe structures and wooden shacks.

The avalanche of water carried several automobiles about 50 yards, officials said.