West London residents have been put on standby following the discovery of what could be an unexploded wartime bomb.
Army bomb disposal experts are trying to identify the object
Builders working on the White City redevelopment found "an object" during excavation work on Thursday.
Police say it could yet turn out to be harmless, but Army bomb disposal experts are trying to identify it.
They have warned a substantial number of homes could be evacuated on Saturday if it turns out to be a bomb that needs to be made safe.
"We would like to reassure the public that the situation is in the hands of experienced professionals," said a Scotland Yard spokesman.
"Contingency measures have been put in place should the object need to be exploded in a controlled setting.
"The safety of the public is paramount at all times."
Travel advice for football fans
"If the object proves to be an unexploded World War II bomb, we are working on the assumption that making it safe will take 48 hours or possibly longer."
Wood Lane and part of the Underground Central Line could close, traffic would be restricted and the old White City London Transport depot area could be cordoned off from 0800 GMT on Saturday.
Football fans heading to Fulham's match at Loftus Road on Saturday are advised to check for information and try to avoid Wood Lane and the Central Line.
The object was found during work on a massive retail, leisure and housing development in White City.
The London Borough of Hammersmith and Fulham has a telephone number for updates - 020 8753 3100.