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Six people were injured and up to 150 houses were damaged when a tornado swept through several London streets leaving a trail of destruction.
Rooftops were ripped off and cars were badly damaged as the freak weather hit the Kensal Rise area.
One man suffered a serious head injury and five people were treated at the scene for minor injuries and shock.
Fire services have sealed six roads in a zone covering a quarter of a square mile and searched 100 properties.
Fire crews were called at about 1100 BST on Thursday to Chamberlayne Road and surrounding streets, amid reports of collapsed scaffolding and damage to buildings.
Witnesses said there was heavy rain and sleet, then debris flying through the air.
Resident Colin Brewer said: "It was really, really incredible. All of a sudden I saw a swirl starting to form and then, it was amazing, but it then touched land.
"I then saw clumps of all sorts of things flying into air.
"It went from exciting to terrifying."
He reported seeing trees ripped up from the roots, front doors missing, windows smashed and people being hit on the head by flying objects.
Seven London Ambulance Service (LAS) vehicles were sent to the scene.
LAS said a man, thought to be in his 50s, was treated for a head injury and five others were treated for shock and minor injuries at the scene.
Dave Bonner, of the London Fire Brigade, said about 50 fire fighters have searched over 100 properties and found several people injured.
Residents will not be allowed to return to their homes until the area is deemed safe.
Brent Council has set up a respite centre at the nearby Church of the Transfiguration for residents who have been made temporarily homeless.
"The council has sent officers, including tree and building experts, and contractors, to help with removing fallen trees and damaged properties," said a council statement.
Transport for London said a number 52 bus was caught up in the tornado.
A spokesperson said: "The windscreen of the bus was damaged. No-one was hurt and the bus has now gone back to the garage."