North Belfast bomb alert could continue overnight
Police have said it could be Thursday morning before the Antrim Road in north Belfast is reopened.
A large bomb - believed to have been left by dissident republicans - is being examined by the Army on the road.
An alert started after calls claiming to be from dissident republican group Oglaigh na hEireann.
Up to 100 homes and businesses have been evacuated. The road has been closed since 1600 GMT on Tuesday.
The alert is close to Antrim Road police station.
Police are advising motorists to avoid the area where possible and use alternative routes such as the Shore Road, the M2 and the Crumlin Road.
Army bomb disposal experts are still examining the device and have carried out controlled explosions on a suspect car.
PSNI Chief Superintendent Mark Hamilton said: "There's no way I'm going to be opening the road again until I'm sure that there's no risk of death or injury to anybody living or working in that area of the Antrim Road.
"We've received a number of calls over a 24-hour period and the last one in particular led us to believe we were looking for an unexploded bomb in an unstable condition."
Ch Supt Hamilton said 40 to 50 families had been moved from their homes, while a children's home had also been evacuated and people under sedation in a clinic had to be moved.
He said dissident republicans were likely to be responsible.
"The people we're dealing with want to wreck this community - they live in this community but they want to wreck it. They want to kill people in the community, they want to kill police officers," he said.
"If this turns out to be a real device, it's madness, because it will have been lying there and hundreds of people will have walked past it."
Some families who were moved from their homes were put up at Fortwilliam and McCrory Presbyterian Church overnight.
The Reverend Lesley Carroll said the alert had been "very disruptive".
North Belfast MP Nigel Dodds said those responsible had nothing to offer society.
"Whether or not there is actually a device, this is a grossly irresponsible act designed to cause severe disruption to the residents of this mixed area," he said.
"Those responsible prove only how totally inconsiderate they are of other people's well-being and I condemn their actions utterly."
Sinn Fein MLA Gerry Kelly said police had received three coded warnings. But he said the calls were very confusing.
"They said there was a bomb within the distance of some mile along the Antrim Road. That was checked out," Mr Kelly said.
"In a second phone call, they said it was somewhere on the Antrim Road and in the third phone call it has been narrowed down to somewhere around the Glandore area.
"They said in their latest phone call it was in a dangerous condition. We need to know where that is so that something can be done about it."
Meanwhile in a separate development, police investigating dissident republican activity in County Tyrone have arrested a man.
The 48-year-old was detained in Strabane on Wednesday morning.