Schools and homes have been evacuated after a Second World War bomb was discovered on a building site.
Army bomb disposal experts are on the scene after the unexploded device was found in Brent, north-west London.
Work on the site is expected to continue until at least Friday afternoon, Brent Council said.
A police cordon has been established at the scene and will be extended to around 300m on Friday morning, forcing more residents to leave their homes.
More than 50 people are currently staying at a rest centre set up at St Martin's Church on Mortimer Road, Kensal Green.
Several British Red Cross volunteers are on hand to provide support to affected residents.
Scotland Yard said it was called to The Avenue, near Brondesbury Park, at around 11.30am on Thursday following the discovery.
Nearby schools, businesses and residents were evacuated and roads closed.
Superintendent Nigel Quantrell said: "I would like to thank the community for their continued support as we and our partners deal with this incident.
"I can assure you that we are working very hard to resolve the situation. The public's understanding and cooperation is deeply appreciated."