Two men died and four others were injured in a crash on the M1 in the early hours of this morning.
The East of England Ambulance Service were called to the crash involving two black BMWs between Watford and Edgware at 2.45am.
Six ambulances, two fast response cars and a hazardous area unit were sent to the scene, near junction five (Watford).
The driver and the front seat passenger of one of the cars died at the scene.
Two of the injured men were stabilised and taken to St Mary's Hospital in Paddington with serious injures.
Another two men also suffered injuries and were taken to Watford General Hospital for further treatment.
The M1 remains closed southbound between junctions five and four (Edgware) as investigations continue and Herts Police says it is not expected to re-open until mid-morning.
The closure is causing severe delays on the road network entering London.
EEAST spokesman Gary Sanderson said: "First and foremost our thoughts are with the families of all involved."