Royal Navy bomb disposal specialists are dealing with a 2.5m (8ft) device.
More than 2,600 households have been evacuated after an unexploded World War Two bomb was found in Exeter.
Officers were called to University of Exeter halls of residence on Glenthorne Road at about 09:20 GMT on Friday and declared a major incident.
Hundreds of students were initially evacuated from 12 halls of residence after the explosive was found.
Devon and Cornwall Police said army bomb specialists were dealing with the device.
On Twitter, the university said the device was discovered by “builders on private land” next to the Streatham campus.
An initial cordon of 330ft (100m) was extended to 1,310ft (400m) on Saturday morning and people in about 2,600 households have been told to move.
Bomb disposal experts started examining the device at about 10:00 GMT on Saturday to decide how to deal with it.
Insp Sean Roper, of Devon and Cornwall Police, said resolving the situation would “take some time” because of the “considerable size” of the bomb.
The explosive device is estimated to be about 8ft long (2.5m).
Police said they hoped the operation would be completed “by the end of today … but will be guided by the bomb disposal team”.
The force added: “Residents should be reassured that military, police and partners are working to maintain public safety.”
The BBC’s John Ayres said there had been “unusual scenes” of “hundreds of students with suitcases, all marching down the street towards St David’s [railway] Station, away from the university and finding somewhere to go”.
One student, Lucy, told the BBC she was in a hall just over 330ft (100m) away from the scene when she and neighbours were told to leave at about 18:00 on Friday, given dinner and moved to hotels.
She said: “We’ve been told we’ll be staying here until Sunday.”
She added: “I didn’t think it was that big a deal until I realised how big it was and how people were taking it so seriously.”
The university said it would “support those who are affected until the situation is resolved and buildings are reopened”.
It said: “We will communicate directly later today by email with those students who have been relocated.”
The university said on Friday night it could not say exactly how many students were moved as “obviously many students are not back on campus because of the Covid-19 situation”.
Coastguard rescue officers, volunteers from Dartmoor Search and Rescue and members of disaster response charity Re:Act were among workers helping with the evacuation.
Re:Act said the evacuations were completed by about 11:00.
Exeter City Council said no evacuation centres had been set up and people affected had been encouraged to stay with relatives.
Roads have been closed in the area and city rail services disrupted as a result of the discovery.
The city was heavily attacked by German bombers in 19 raids during World War Two, particularly in May 1942 during the Baedecker Raids.
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