A dam collapsed in western Kenya early Monday, killing at least 40 people after a wall of water swept through houses and cut off a major road, police said.

The Old Kijabe Dam, located in the Mai Mahiu area of the Great Rift Valley region that is prone to flash floods, collapsed and water spilled downstream, carrying with it mud, rocks and uprooted trees, police official Stephen Kirui told The Associated Press.

Vehicles were entangled in the debris on one of Kenya’s busiest highways and…