Two men died at the scene of a crash in East Ardsley, with two men still in a critical condition in hospital.
A black Volkswagen Golf had been involved in a collision with a black Ford Focus and a silver Mercedes C220.
Two men, aged 26 and 34, who were rear seat passengers in the Golf, were pronounced dead at the scene.
Two of the men, aged 25 and 33, are currently described as being in a critical condition.
A 17-year-old boy is also receiving medical treatment.
They were all in the Golf.
The driver of the Mercedes, a 59-year-old man, was treated for a fractured wrist.
The Golf was travelling away from the M1 towards Leeds at the time of the crash.
The road was closed until 2.30pm while police conducted their investigations.
Detective Sergeant Alison Webb, of West Yorkshire Police Major Collision Enquiry Team, said: “This collision has very sadly resulted in the deaths of two men, and the other occupants of the Golf are currently undergoing emergency treatment in hospital.
“We are doing everything we can to support the families of those involved at what is clearly a very difficult time for them.
“We are carrying out a comprehensive investigation to establish the full circumstances of this incident and would like to hear from anyone who witnessed either the collision itself or the movements of the vehicles involved in the time leading up to it.
“We are particularly keen to hear from anyone who has any relevant dashcam footage which could assist the investigation.”
Anyone with information is asked to contact the Major Collision Enquiry Team via 101 quoting Operation Pivotford or reference 13190322436.