Thousands of residents have been evacuated in Plymouth, southwest England, as authorities work to remove an unexploded 500-kilogram (1,102-pound) bomb discovered in the city.

Authorities announced plans to move the bomb, thought to date from World War II, from its location at St. Michael Avenue and transport it in a military convoy to the city’s Torpoint Ferry slipway, in what Britain’s Ministry of Defence described on Twitter as “one of the largest UK peacetime evacuation operations since WW2,” with a 300-meter (984-foot) cordon established around the route.

The bomb will then be disposed of at sea, Plymouth City Council said Friday. It was discovered in a garden in the city’s Keyham area.

“After the expert assessment, it became apparent that if a controlled detonation was carried out in situ, there would be too high a risk of significant damage to properties in Keyham, including destroying a number of houses and flying debris which would potentially damage a wide number of properties,” the council explained on its website.

“There is obviously an element of risk. It’s been assessed by the army who have deemed this is the lowest risk,” Superintendent Phil Williams of Devon and Cornwall Police said during a press conference.

Residents were instructed to leave their homes by 2 p.m. local time (9 a.m. ET) and were expected to be allowed to return three hours later.

Authorities added that the city’s trainline would be closed, ferries suspended and buses diverted.