Police are urging anyone who witnessed the scene, near junction 5 and 6 at Kirk o’ Shotts, to contact them.
The incident happened around 3.30pm yesterday, when a blue Audi A4 collided with the central crash barrier, crossed the carriageway and hit a Subaru Impreza car.
A 44-year-old man who was a passenger in the Audi died at the scene. The 25-year-old male driver and a 21-year-old male passenger were slightly injured.
The 27-year-old male driver of the Subaru was treated for slight injuries, but two women passengers aged 29 and 26 suffered serious injuries and are “serious but stable” in Edinburgh Royal Infirmary.
During the emergency an air ambulance landed on the carriageway to ferry the casualties to hospital.
The motorway was closed in both directions for around six hours following the crash.
Appealing for witnesses, police are also asking anyone with dash cam footage to get in touch immediately via 101, quoting
incident number 2953 of July 27 2019.