A 31-year-old woman has died after the car she was travelling in hit the central reservation of the M1 in Hertfordshire.
Police said a Vauxhall Vectra had been heading south on Tuesday night when it seemed to lose control and hit the barrier at junction five, near Watford.
It rebounded into the carriageway and collided with a silver BMW.
All four people in the red Vectra were from Liverpool. The driver, a 39-year old-man, sustained minor injuries.
A 21-year-old woman who was in the back seat also suffered minor injuries and a 34-year-old man in the front seat was uninjured.
Three men from London were travelling in the BMW. The driver was treated for minor injuries.
Appeal to driver
A red Toyota Celica lost control during the incident and it is unclear whether it was in collision with the Vectra, police said.
The Celica crossed the carriageway to the nearside and went up the embankment. The driver has not yet been traced.
Pc Ian Breacher said: "This was a serious collision in appalling weather conditions, in which one lady tragically lost her life.
"We are appealing to anyone who was travelling on the motorway at about 2100 BST and who may have witnessed the collisions to get in touch.
"We are also appealing for the driver of the Toyota Celica to make contact with the police."
The motorway was closed for several hours.