More than 400 homes in the county town of Newtdowns have been evacuated following the discovery of a World War II bomb, police said.
It was found on a construction site In the Rivenwood housing development Friday on Movilla Road.
A police cordon has been put in place at the top of Rivenwood Road where new houses are being built.
A bomb disposal unit is currently on site, with military personnel using excavators to pile sand on top of the device ahead of a planned controlled detonation.
Superintendent Johnston McDowell, North Town and Arts District Commander, said: “This is a significant number of properties and we thank residents for their patience and understanding.
“I would like to say that unless the police have directly spoken to the homeowners or residents or received information regarding this matter, it is unlikely that they will be affected by the sanctioning action at this time.
“At this stage the operation is expected to continue for several days.
Stephanie lives near where the bomb was found and said the evacuation was “very disruptive”.
“I'm starting a new job tomorrow and it's really hard to find the place I've been staying, and then it's really hard to find somewhere for my pets, so it's been really stressful,” she said.
“We don't know if there will be damage to our property, and we have no guidance on how to protect our homes to minimize any damage.”
On Saturday evening, the Police Service of Northern Ireland (PSNI) issued a leaflet asking residents to leave their homes by 10:00 BST on Sunday due to “danger to life and property”.
The report added that all homes and businesses within a 400m (0.25 mile) radius were affected by “a large amount” of explosives and that the operation could take “five or more days”.
A steady stream of cars left the development on Sunday morning.
Some residents are staying with family, including newlyweds Andrew and Sarah Lightbody, who married a fortnight ago.
They told BBC News NI that a police officer phoned their door on Saturday night and told them to leave by 10:00 BST on Sunday.
They packed their dogs and some personal items.
James Fraser, the developer of the site, said the suspicious device was found by workers during some ground work for a new phase of development where 40 homes were being built.