Hundreds of people may have to spend a second night away from their homes after a suspected unexploded World War Two bomb was discovered in Bath.
Up to 1,000 homes have been evacuated and a 300m exclusion zone is in place following the find in Lansdown Road.
According to reports, a 500lb (228kg) bomb was found just a metre beneath a playground at the former Royal High Junior School.
Residents have been evacuated to Bath Racecourse for up to 48 hours.
The device was discovered at about 16:40 BST on Thursday by contractors using a digger at the former school, which had been in use until a few years ago.
Avon and Somerset Police said the Explosive Ordnance Disposal (EOD) team had attended the site.
"The EOD are currently building a barrier around the device using 250 tonnes of sand," a spokesman said.
"Once this barrier is in place, they will remove the device with a police escort to a safe location away from the Bath area, where they will carry out a controlled explosion."
He added that residents "outside the exclusion zone" would be unable to re-enter for up to 48 hours, while those who remained inside the cordon were being prevented from moving within 100m of the device.
Robin Squire, from Acorn Properties which has been working on the school site, said there had been "a history of bombs in the area" and "all the relevant surveys" had been carried out.
"It was actually in an area we wouldn't expect to find anything - not that we necessarily expect to find a bomb," he said.
"But people on site were warned what to look for and then basically we had to put the situation in the hands of the police and the Army."
Bob Lawrence, who stayed overnight at Bath racecourse, said he had been looked after "very well".
"I was walking back from the pub - up Lansdown Road - and the people in front of us got turned back by the police but we took another route home," he said.
"At about 9 o'clock we got a knock on the door and the police advised to evacuate. A couple of our neighbours decided to stay there but the rest of us moved out."
But Glyn, who lives "about 150 yards away from where the said bomb is", decided to remain at home.
"To be fair the bomb's been there for 70 years," he said.
"I've lived long enough with that bomb next to me and if it was going to go off, it would have gone off by now."
The Bath Blitz took place in April 1942, and was part of the Baekdeker raids by the German air force in which targets were chosen due to their cultural and historical status.
Michelle Carpenter said she had been allowed back into the area briefly by police.
"When I got to my flat at about 8 o'clock, the police said I couldn't have access so I've spent the night with my boyfriend." she said.
"But this morning the police told me I could come in [to my flat] for a few minutes just to get some stuff that I need for the day."
Ch Insp Kevin Thatcher has urged "people not to be alarmed".
"The EOD are working as quickly as they can to remove the device and we will provide regular updates on their progress," he said.
A Bath & North East Somerset Council spokesman said: "Schools close to the cordon may be affected and the advice is to consult the council website, Twitter feed, local radio stations, as well as look out for messages from the schools themselves."
Motorists have been asked to find alternative routes as some roads in the area are closed.