Watch ITV News West Country's interview with Police Inspector Sean Roper at the scene
Police say people may not be able to return to their homes until tomorrow after "quite a large" unexploded bomb was discovered in Exeter.
A major incident was declared after the discovery of the suspected World War Two bomb.
Around 100 properties have been evacuated and the military has been brought in to make the device safe and remove it.
Police say it's not unusual to find unexploded devices in Devon, but one of this size is "uncommon".
Police Inspector Sean Roper, who is the critical incident manager at the scene, told ITV News West Country: "Police were given a call at 9.20am from a construction firm who were working just off of Clydesdale Road.
"They found quite a large ordnance."
Insp Roper added: "It's approximately 2.5m in length by about 70cm in width.
"It's not uncommon for this area, to find World War Two explosives - but one of this kind is uncommon so we're taking all the precautions we need to to make sure everyone is safe in the area.
"We're fully aware that this is probably decades old but the moving of this item does pose a risk and we need to make sure we do everything we can to support the locals."
When asked how long it might take to remove the device, Insp Roper said: "At the moment the item is uncovered and the explosive specialists are reviewing it now. The issue they have with it is deciding how they will tactically deal with the item safely.
"What we do know is it's likely to go into tomorrow."