North Yorkshire Police said at around 4.30am this morning (Oct 18) that they had closed the round in the southbound direction between junction 51 and 50.
The force said the crash happened at around 2.20am, and said the road was expected to be closed for 'several hours'.
Highways England said they were at the scene and working to reopen the road but they did not have a timescale for when that might happen.
They tweeted: "Please be aware that this #A1M southbound J51 - J50 incident is causing delays of 40 mins above normal journey time for this time of day. There is approx. 4 miles of congestion on approach. Please allow plenty of extra time for your journey if you are travelling in the area.
Police said anyone who may have witnessed the crash, or have any information, should call them on 101.
Support The Yorkshire Post and become a subscriber today. Your subscription will help us to continue to bring quality news to the people of Yorkshire. In return, you'll see fewer ads on site, get free access to our app and receive exclusive members-only offers. Click here to subscribe.