According to Lincolnshire Police, the inside westbound lane of the busy dual carriageway between the Mount Lane, Kirkby la Thorpe turn off and the Bonemill Lane junction onto East Road has had to be closed by emergency services to allow firefighters to tackle the flames.
No-one is said to have been injured in the incident.
The incident was reported at about 1.45pm.
It is causing some hold ups, affecting traffic heading from Heckington towards Sleaford and you are advised to avoid the area if possible.
It is unknown how long the road will be blocked.