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
The employee was sorting through rubbish at waste company Amey's Waterbeach facility.
Ice is expected to form on some surfaces from late Tuesday afternoon and last overnight into Wednesday morning.
Ian Tang was last seen at 2.30am on Sunday leaving the KA club in North Walsham.