The stand-off between police and a man with 'dangerous items' on Wood End Lane in Northolt enters a third day.
An operation by Ealing police has been under way since Friday (October 21), following a report made to police concerning a resident with quantities of petrol and combustible material inside the property.
Police believe the man may be experiencing mental health issues, making his behaviour unpredictable.
So far officers have not attempted to enter the house and the Metropolitan Police say "it may take some time" to bring the situation to a safe end.
Armed police and negotiators are assisting officers who continue to treat the situation seriously and hope to bring the incident to a safe conclusion.
Roads in the area remain closed and buses have been placed on diversion.
It is believed the man is alone inside the property and attempts have been made to prevent access to the building.
Due to safety concerns around 80 people have been forced to move out of their homes into temporarily accommodation with help from Ealing Council , and the 200 metre police cordons remain in place.
Ealing police chief superintendent Paul Martin, said: "Our aim is to bring this to a safe conclusion for everyone.
"I know that our operation has been ongoing for some time now and that it is causing disruption and inconvenience to local residents and the community of Northolt.
"I would like to thank them for their continued patience and cooperation. I can understand why people may be feeling frustrated or concerned.
"The operation will continue for as long as is necessary and I would like to stress that we are doing all we can - using all our tactics - to end this incident safely."
Officers are on duty to speak to local people and assistance is being provided by the London Ambulance Service; London Fire Brigade and the local authority.
Leader of Ealing Council, Julian Bell, said: “We are working closely with our colleagues in the police as they continue to deal with the ongoing incident in Northolt.
“I’ve been kept appraised by the police throughout the incident and we have offered help to those residents who have had to leave their homes.
“The safety of our residents is our top priority and council officers will continue to be on hand to give any necessary assistance until the incident has been resolved.”
Police say the incident is not terrorist-related or linked to any other ongoing police operation.
