Roads and Transport Policing officers are appealing for witnesses to a serious collision in Hounslow on Saturday, 28 May.
Police were called by the London Ambulance Service (LAS) shortly after 01:00 hours to reports of a collision involving a mini-cab and a van at Whitton Road junction with Station Road.
Officers and the LAS attended along with the London Fire Brigade.
The driver of the mini-cab, a 44-year-old man along with a female and male passenger (female - aged 25 and male - aged 27) were found injured at the location.
The driver of the van, a 27-year-old man had to be cut out of his vehicle after it had collided with a lamppost following the collision with the mini-cab.
All four casualties were taken to hospital, their injuries are not being treated as life threatening. No arrests have been made.
Officers have established that the mini-cab (a blue Ford Galaxy people carrier) had picked up two passengers from Whitton Road shortly before the collision occurred. The mini-cab drove south and was negotiating the right hand turn into Station Road when the van (a white Volkswagen Caddy) travelling northbound collided with the mini-cab. After colliding with the vehicle, the van then collided with a lamppost.
The driver of the van was also carrying a male passenger who left the scene prior to police arrival and he is believed to be injured. Officers are concerned for his welfare and are keen to trace him to ensure he receives medical attention.
Any witnesses or anyone with any information that can help trace the passenger of the van is asked to call the Serious Collision Investigation Unit on 020 8542 5157.