There is understood to be a 100m cordon in place around Grand Arcade in Cambridge following reports of a suspicious package.
Bomb disposal teams have been dispatched, police are expected to be in the area for several hours.
More top news
Clear skies for a time tonight before low cloud, mist and fog returns
Govia Thameslink has taken over services on First Capital Connect routes promising more trains and better punctuality.
Coroner records narrative verdict on death of Latvian teenager on Sandringham estate