Two people were killed in a car that drove down the wrong side of the road and hit a coach following a lengthy police pursuit in west London.
The man and woman died on the A40 in Acton, at about 21:00 GMT on Sunday.
A second man was hurt in the crash, which took place after the pursuit began seven miles away in Harrow after reports of an armed burglary.
The Met Police said its officers did not follow when the car went down the wrong side of the A40.
Fire and ambulance crews, along with the police helicopter, were called in and roads in the area - near the A40's junction with Kingsdown Avenue - were closed.
Transport for London said the roads reopened in both directions at 07:45.
The crash happened about 20 minutes after the police pursuit began.
Witness Antoine Eid, 47, said "it wasn't like a normal car accident", and there was "no chance" of the coach slowing down before the crash.
"I've never seen something like that," he added.
The second man was taken to a major trauma centre, although the extent of his injuries have not been confirmed.
There were no reports of any other serious injuries, the Met said.
The Directorate of Professional Standards and the Independent Office for Police Conduct (IOPC) have been informed.
IOPC regional director Jonathan Green said: "My thoughts are with the families and friends of the two people who have died, those injured and all those affected by this incident.
"It is important that we now establish all of the circumstances surrounding this collision.
"We have therefore launched an independent investigation into the events leading to the collision and have immediately deployed our investigators to attend the scene and the post incident procedure where further information will be gathered."
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The chase came after police were called to reports of an aggravated burglary in Pinner, Harrow, at about 20:40.
A man in his mid 30s, a woman in her late 50s and a man in his late 60s said the door to their home was forced open and four men entered.
The suspects then threatened them with a large hunting knife and screwdriver and demanded valuables.
Police said the suspects threatened to kill the residents and one punched the man in his 30s in the face.
The suspects left taking cash and jewellery.
The IOPC is investigating four deaths in separate incidents involving police vehicles, within four days of each other, in January.
There were 29 police-related fatalities on the roads in 2017-18, of which 17 were "pursuit-related", according to the IOPC.
Eight involved police vehicles responding to emergency calls.
Five deaths involved police vehicles hitting pedestrians while responding to an emergency call and one pedestrian death related to a pursuit.
In the previous year, 2016-17, there were 32 fatalities on the roads involving the police. Of those, 28 related to pursuits and none involved police responding to emergency calls.
- 23 January 2019