It is shut between the Long Hedges turn-off and Pilleys Lane, north of Boston. Traffic between the town and nearby Sibsey is worst affected and motorists are queueing, though they can pass through.
The closure was first reported around 2pm on Thursday, October 12. Google Maps is showing bad congestion along the main road, though connecting routes appear to be coping well.
The extent of any injuries has not been confirmed. There is a diversion route in place by way of the Brylaine bus service B4.
Lincolnshire Police has been contacted for more information.
This is a breaking news event and we will bring live updates as they come in.