LONDON (AP) — Heavy rain was forecast Sunday for the area around a damaged reservoir in northwest England as emergency crews raced to pump out water to prevent the dam from failing and a town from being flooded.

Britain's meteorological agency said "torrential downpours and hail" were possible across northern England, hampering the emergency work to reduce the water level in the 180-year-old Toddbrook Reservoir.

About 1,500 residents were evacuated from Whaley Bridge, a town 175 miles (280 kilometers) northwest of London, after part of the reservoir's spillway gave way last week.

Another 55 homes were evacuated Saturday due to concerns about the weather and "the ongoing risk of the Toddbrook Reservoir breaching," Derbyshire police said.

Police stopped allowing evacuated residents to stop by their homes for supplies, saying officers needed to focus on the pending storm and potential flooding.

"The attention of officers and other responders has to be on the preservation of life," Derbyshire police said in a statement. "While there was an urgent need over the past 24 hours to allow residents back into the area, our first duty is to protect the lives of the public and emergency services."

Forecasters said as much as 40 millimeters (1.6 inches) of rain could fall in one to two hours, according to Britain's Met Office.

Since the dam was damaged last week from heavy rains that sent torrents of water rushing over the spillway, a Royal Air Force helicopter dropped some 400 one-ton bags of sand and gravel into a gaping hole in the spillway. Contractors worked to bind the bags together with concrete grouting.

Firefighters say 22 pumps were working around the clock to pull water out of the reservoir and into the River Goyt to ease pressure on the dam.

Derbyshire deputy fire chief Gavin Tomlinson said about 35% of the water in the reservoir had been removed by Sunday morning. Inlets into the reservoir were also being dammed off to block any floodwaters from the expected rain.

"The dam is like a bowl, it doesn't have straight sides, so as the water level drops crews are having to relocate the pumps to ensure they are able to work as effectively as possible," Tomlinson said. "Our priority remains the same, to pump as much water out of the reservoir as possible, to protect the Whaley Bridge community from the risk of the dam failing."