Residents from more than 1,500 homes are being advised to move out after a 500lb (227kg) World War II bomb was found in the back garden of a house.
Bomb disposal experts are at the scene in Friars Road in Mudeford
The unexploded German bomb was dug up in Christchurch, Dorset, on Friday morning by builders laying the foundations for an extension.
People from the nearest 250 homes were told to leave immediately while army bomb disposal experts were brought in.
Police have now increased the exclusion zone to about 600yds (nearly 600m).
A spokesman for Dorset Police said the additional householders were not being ordered to evacuate, but advised to leave their properties by 1500 BST as a safety precaution in case the device explodes.
The team of Royal Engineers has been at the scene in Mudeford since Friday afternoon, but police are unable to say how long it will be before residents can return to their homes.
Joe and Lilian Morgan were told to evacuate their home around the corner from where the bomb was found, on Friday night.
Mrs Morgan said the police came and knocked on the door while she was cleaning and her husband was in the garden.
Residents from about 1,500 homes have been advised to move out
She said: "We gathered a few things together. He [Mr Morgan] packed a little case with socks and a few things and then we were off.
"I didn't like it at all but I wasn't worried about the bomb somehow, as long as we got away."
Sara Kerr, who also lives in Mudeford, said she was not too worried: "If it's been there for 60 years I'm sure it can stay there for a bit longer until it's actually dealt with."
Evacuees can go to the Two Riversmeet leisure centre in Stony Lane where Christchurch Borough Council has set up facilities. Some people are also being put up in local Bed and Breakfasts.
A letter advising residents of what to do has been delivered to homes within the exclusion zone.