Families were evacuated on Monday night when workmen discovered a 450kg World War II bomb in the grounds of a medical centre in the Hendon area of Sunderland.

On Monday night about 500 people were cared for in two local schools, others at a day care centre, and many more went to stay with relatives and friends.

It was hoped the bomb could be defused on Tuesday but it was decided the device was too unstable to treat until further equipment was brought to the scene.

Mechanical digger

The bomb, thought to have been dropped by a German Heinkel bomber in 1940, may not now be defused for another two or three days.

A further 2,000 people have refused to leave their homes, despite police appeals and warnings that the 60-year-old bomb is unstable.

The bomb was accidentally reactivated after being dug up by workmen using a mechanical digger.

Army authorities, who are monitoring the situation, may advise a compulsory evacuation.

We are treating this very seriously, which is why we have a 400m area cordoned off and so many people have been evacuated from the area

Superintendent Paul Weir

Bomb disposal experts at the site in Suffolk Street, Hendon, have dug a large crater around the bomb - which is not on a timer - to pack it with sandbags.

It is not known how long it will take to defuse the bomb, which is described as being the size of an oil barrel.

A 400m exclusion zone was set up, with roads closed and train services suspended and a number of schools have also been closed.

Superintendent Paul Weir, of Sunderland Police, said: "The bomb was almost excavated behind the health centre at about 1700 BST.

"We immediately started evacuating... we took advice from army experts who then extended that area.

Severe disruption

"It is a 450kg bomb with 200kg of explosive in it.

"We are treating this very seriously, which is why we have a 400m area cordoned off and so many people have been evacuated from the area.

"The military are trying to stabilise the bomb. They are trying to put some safety measures around it and then defuse it, but that is some time away.

"It's most likely to cause severe disruption and some of the schools in the area are going to have to remain closed."