DENVER (AP) — Flash flooding in northern Colorado has left two people dead. Widespread high waters are keeping rescuers teams from reaching stranded residents and motorists in Boulder and nearby mountain communities as heavy rains hammer the area.

The University of Colorado shut down classes. Hundreds were evacuated from family housing.

Boulder Office of Emergency Management spokeswoman Gabrielle Boerkircher says volunteers are trying to help stranded people until emergency crews can arrive because many roads are impassable.

Boerkircher says one person died when a structure collapsed in Jamestown. Colorado Springs spokeswoman Kim Melchor says police found another person dead in the water on the city’s west side.

National Weather Service meteorologist Bob Kleyla ays a 20-foot wall of water was reported in Left Hand Canyon north of Boulder. He says a firefighter radioed he was trapped in a tree, and rescuers were trying to get through.