Torrential rains unleashed deadly flash floods along the Guadalupe River in south-central Texas on Friday, killing at least 13 people and leaving nearly two-dozen girls reported missing from a riverfront summer camp,

Officials said as many as 13 bodies have been found and 23 girls from Camp Mystic, a private Christian girls’ camp, have not been accounted for after a catastrophic flood that swept through Kerr County overnight Friday morning.

These factors, especially in the Balcones Escarpment landscape in Central Texas, make Flash Flood Alley one of the most flood-prone regions in North America.