BBCPolice say more than 400 homes have been evacuated in Newtownards, County Down, following the discovery of a suspected World War Two bomb.
It was found at a building site at the Rivenwood housing development in Movilla Road on Friday.
A police cordon is in place at the top of Rivenwood Road, where new houses are under construction.
A bomb disposal unit is currently on site, with Army personnel using diggers to pile sand on top of the device ahead of a planned controlled explosion.
North Down and Ards District Commander Superintendent Johnston McDowell said: “This is a significant number of properties, and we thank residents for their patience and understanding.
“I would like to state that if home owners or residents have not been spoken to directly by police, or received information in relation to this matter, it’s unlikely that they will be impacted by the clearance operation at this time.
“It is anticipated at this stage that the operation will continue for a number of days.”
It is unclear what type of bomb the device is, but Belfast was bombed heavily by the Luftwaffe in April and May 1941 during World War Two.
Bombs were also deliberately or mistakenly dropped in other areas of Northern Ireland.
Rivenwood resident David Lewis told BBC News NI about the disruption he and his young family are facing.
”We’ve had to stay with my mum and dad, they’ve a 2-bedroom bungalow and there are five of us living with them along with the dogs,” he said.
“Our two dogs have been relegated to a shed, we will be living in the one bedroom.’’
“We’ve packed up the whole house, literally everything.”
Mr Lewis said a “sore point” was the lack of information he had received.
He added: ‘’Our daughter learnt about WW2 and was exited at the start because they found something from the war near the house, now she realises what’s happening she’s petrified.’’
Stephanie O’Fee lives near to where the bomb was discovered and said the evacuation has been “very disruptive”.
“I’m starting a new job tomorrow and it’s been very hard to find somewhere that I’ve been been able to stay and then finding somewhere for my pets as well, so it has been pretty stressful,” she said.
“We don’t know if there is going to be damage to our properties, and there’s been no guidance to how to secure our homes to lessen any damage.”
OtherOn Saturday evening, the Police Service of Northern Ireland (PSNI) issued a leaflet to residents requesting them to leave their homes by 10:00 BST on Sunday due to the “possibility of risk to life and property”.
The statement added that all homes and businesses within a 400m (0.25 miles) radius of the “sizeable” munition were impacted and that the operation could take “five or more days to complete”.
A steady stream of cars left the development on Sunday morning.
Some residents are going to stay with family, including newlyweds Andrew and Sara Lightbody, who got married just a fortnight ago.
They told BBC News NI that a police officer called at their door on Saturday night and told them to evacuate by 10:00 BST on Sunday.
They have packed their dogs and a few personal items.
James Fraser, the developer of the site, said the suspected device was discovered by workers during some ground works for a new phase of the development where 40 homes are under construction.
Google MapsDUP MP Jim Shannon, Jim Shannon, told BBC News NI: “If it was to go off it would be devastating, the police’s priority is to ensure it doesn’t.
“The army bomb disposal unit will be very proactive and very positive, their job is to make it safe and thereby let people back into their homes as soon as possible.”
After speaking with residents, UUP MLA Mike Nesbitt, said ”one of the biggest issues is pets”.
“There’s a lot of people who are still in Rivenwood trying to decide whether they’ll breach the police cordon, because they’re concerned about their pets in the short term.”
The Ards Blair Mayne leisure centre has been set up as an emergency support centre for affected residents.
Alliance MLA Nick Mathison said “anyone with vulnerabilities due to health, age, or who requires access to medication should seek help from the Ards Centre”.
In February, a World War Two shell was found in County Londonderry and destroyed by ammunition technical officers in a controlled explosion.
Another unexploded wartime-era device was destroyed by controlled explosion in County Armagh in January.
The device was found in Woodlawn Heights in Richhill.
Earlier this year, a 500kg (1,102lb) German World War Two bomb forced the evacuation of thousands of people in Plymouth.
