Armed police have been called to a property in Northolt following reports of a man with hazardous items inside. The London Ambulance Service, London Fire Brigade, local authority and the police are working together after being called in the early hours of Friday morning.
Police did not attempt to enter the property on Wood Lane End but put in place a 200 metre radius cordon.
Around 80 people have been re-housed from the immediate area of the address.
While it is not known what the man has inside the property officers are said to be treating the reports that the items could be dangerous seriously.
It is not thought that the incident is terror related.