A 21-year-old woman was killed in a head-on crash with a van which had failed to stop for police near Dagenham.
The van, which was travelling in the wrong direction of the Essex-bound carriageway on the A13 collided with a black Toyota Prius.
The woman, who was a passenger in the Prius, was pronounced dead the scene.
The driver of the van, 39, was taken to hospital for treatment where he remains there in a serious condition.
He has been arrested on suspicion of failing to stop for police and causing death by dangerous driving.
The driver of the Prius attended hospital but is not thought to be seriously injured in the incident at 02.35am on Friday,
The Independent Office for Police Conduct (IOPC) will be investigating the circumstances surrounding this incident including the involvement of Essex Police officers prior to the crash.
Detective Sergeant Mike Rapp said: “This is a terrible incident that has resulted in the tragic death of a young woman.
“I am appealing for anyone who was driving on the A13 in the Dagenham area shortly after 02:30hrs and saw the events unfolding as this van drove on the wrong side of the Essex-bound carriageway to contact us.
“There is footage circulating on social media of this incident that we are aware of; I would ask anyone in possession of footage to think about the family of the woman who has died and consider their feelings before sharing content. I would also urge anyone who has images or footage of the incident to provide these to police so that we can build a comprehensive picture of this collision.”
Anyone with information is asked to call the Serious Collision Investigation Unit on 020 8597 4874.
You can also call police on 101 or tweet @metcc and quote CAD562/25Nov. You can also provide information anonymously to the independent charity Crimestoppers on 0800 555 111.