Residents in 20 flats and ten houses were evacuated late overnight as a dam threatened to burst in Allerton, Bradford, causing heavy traffic this morning.

The dam in a field off Stony Lane contains about 2,000 cubic metres of water and the alarm was raised as it began to spill over.

Three teams of firefighters from Fairweather Green and Stanningley fire stations were called to the scene at 11.30pm and police evacuated people whose homes were in danger of flooding.

Stony Lane, Haworth Road and Wilsden Road were closed.

The operation continued into this morning as Bradford Council engineers continued to monitor the state of the dam.

Sandy Lane Primary School is closed today because of the incident.

Inspector Paul Hepworth, of Bradford North Police, said: "Either the beck has been blocked or the bad weather has built up a large amount of water and is held back by a wall of earth and stone.

"My main priority is preservation of life and property. If it bursts it has the potential to cause major damage and kill people."

Ian Gilchrist, senior operations manager for West Yorkshire Fire and Rescue Service, said: "The water in the lake is the equivalent to ten or 11 Olympic size swimming pools.

"The crews are pumping it out at around 300,000 metres an hour. The high pressure pump is twice the power of a standard pump and it is tipping the water into the beck further down.

"We have moved 15 to 20 per cent so far. Eleven people have been evacuated from the new Croft House and two more people from a neighbouring house. Sandy Lane School is closed as a safety precaution."

Jean Watson, 65, of Grasleigh Way, said: "It's a fishing pond usually, a lot smaller, you wouldn't even see it from the road.

"I've lived here for years and it's never been like this before. The water was pouring down and it did look like the bank would weaken."