British police have closed roads and evacuated hundreds of homes near London's Wembley Stadium as the army works to defuse an unexploded World War II bomb.

The 50-kilogram (110-pound) bomb was discovered by builders working near the stadium. It is believed to have been dropped over London during German bombing raids in the early 1940s.

An army spokesman said the bomb is in a "potentially dangerous condition" and that even under a controlled explosion it could cause significant damage to property and a "genuine risk to life." A cordon has been placed around the site and bomb disposal experts were working Friday to defuse the device.