Firefighters have isolated the ammonia leak in Wisbech and say it is no longer a threat to the public.
Four crews of firefighters wearing gas tight suits have been investigating the leak at a property in Mount Plesant Road after receiving reports at 8.30am today (Wednesday, June 4).
Residents in the area were urged to keep windows and doors closed and avoid the area until further notice.
East of England Ambulance service have sent an ambulance, rapid response vehicle and hazardous area response team. One person has been assessed.