Parts of Westfield shopping centre and nearby buildings were evacuated amid fears an item found was a WW2 bomb.
But people were allowed back into buildings and roads and Tube services reopened near the shopping centre after the item was removed.
And the Metropolitan police told the BBC it was not a bomb as first thought.
The casing, 34cm (13.5 in) in length and 15cm (6in) wide, was found by builders in Ariel Way, off Wood Lane.
Local traffic was diverted causing severe disruption and Tube services in the area were affected.
An unexploded bomb alert in west London caused major disruption - but cordons were lifted when it was found to be just a shell casing, posing no danger.