Officers were called around 3am to reports of a collision involving a HGV and a pedestrian.
A woman in her 30s was hit by a HGV on the southbound carriageway.
The southbound carriageway was closed between Brampton Hut and Wyboston while the HGV was recovered and has now reopened.
The northbound carriageway was closed but reopened at approximately 8am this morning.
Motorists are advised to avoid the area or expect delays.