The M1 remains closed after a man fell from a bridge and then a second man trying to help him, was hit by a car, according to witnesses.
An air ambulance was seen flying to the area following the accident by Junction 6.
Both casualties were reported to have died.
Rebecca Martin, who was travelling northbound on a Megabus, said: "We came to a screeching halt and it sounded like a car accident had happened in front of us or something. We then found out a man had jumped from the bridge in front of us.
"We were just three or four cars behind it. Then another car stopped and a man got out to help and was hit by another car. An air ambulance came and took both of the men away."
She added: "It was quite worrying when we came to a screeching halt and it was quite close to being a massive accident. It’s really bad it’s happened and that someone that was trying to help got run over is just awful."
Police and ambulance services were called to the scene at around 10.50am after receiving calls of concern for the welfare of two people.
The road is closed northbound and police are advising drivers to avoid the area where possible.