People living within 1,300 metres of Grafham Water have been warned to stay in their homes after a chlorine gas leak at an Anglian Water treatment centre. The gas release occurred earlier this evening (Tuesday) at the plant on the B661 in West Perry. A spokesman for Cambridgeshire police said: As a precautionary measure Anglian Water are advising anyone who lives within 1,300 metres of the site to remain indoors and close all external doors, turn off all ventilation and central heating systems. An emergency instruction leaflet from Anglian Water has been given to many residents living in the affected area. Crews from Cambridgeshire Fire and Rescue Service are currently at the scene to tackle the incident. A spokesman for the service said: Work continues at the incident at Grafham Water. The warning siren will be sounding while the work takes place. Residents living in the affected area were told they were able to leave their homes just before 11pm following the leak that was identified by staff on the site. The spokesman added: Residents can be assured that no chemical left the site and the external all clear siren has sounded.