Police were called at about 08:50hrs on Saturday, 7 October to between junctions 24 and 25 following reports that a car – believed to be a dark coloured VW Touran – had collided with a horse box being towed by a van.
The horse box, which was carrying two five-month-old foals, overturned. The driver of the car left the scene.
One of the horses was killed in the collision and the other had to be put down due to injuries it had sustained.
Officers from the Roads and Transport Policing Command are investigating. They would like to speak with anyone who saw the collision or captured it on dash cam.
Anyone with information is asked to call police via 101 quoting reference CAD 1969/07Oct.
There have been no arrests and enquiries continue.