LONDON (AP) — A Royal Air Force helicopter and firefighters are shoring up a reservoir wall in northwest England amid fears that a rain-damaged dam could collapse.

A Chinook is dumping bags of sand and gravel to reinforce a wall of the 19th-century Toddbrook Reservoir as emergency workers use pumps to lower the water level behind the dam.

Hundreds of people were evacuated from the town of Whaley Bridge on Thursday with police officers going door-to-door to notify residents. People in the town, located 175 miles (280 kilometers) northwest of London, were advised to stay with friends and family elsewhere if possible, and to take pets and several days of essential medications with them.

Heavy rains have caused flash floods in many parts of the U.K.