A man who witnessed a serious smash in Kingsnorth, Ashford, is being urged to contact the police.
The collision occurred when a Renault Clio travelling from Hamstreet along the A2070 suddenly veered across the carriageway at about 8.45am last Saturday.
It hit a blue Perodua Kenari GX Estate, which then overturned and burst into flames.
The Clio then careered into the path of a Volkswagen Polo, which suffered only minor damage.
Members of the public were able to turn the Perodua back onto its wheels and extinguished the fire.
Both vehicles suffered extensive front end damage.
The female driver of the Perodua had to be cut free and was flown to a London hospital where she remains with serious injuries.
The driver of the Clio - a man - was taken to the William Harvey Hospital with serious injuries.
Now, officers say they would like to talk to a man who they believe was at the scene.
Senior investigating officer Sergeant Glyn Walker, of the Serious Collision Investigation Unit, said: "Following new information received, we have reason to believe there was a man at the collision scene, immediately post collision, taking photographs of the vehicles and the scene.
"We would urge this man to make himself known to the investigation team to help us build a picture of the circumstances around this collision.
"It is also understood a female nurse attended the scene and assisted. I would also ask her to contact police to assist with our inquiries."
Witnesses should call the Serious Collision Investigation Unit on 01622 798538.