The A1 is closed in between Grantham and Stamford following a crash involving two lorries at just after 1pm.
Traffic is queuing on the northbound section of the carriageway at Colsterworth.
Police are on the scene and the crash appears to be serious at this stage.
However, a spokesperson for Lincolnshire Police said that there were no life-threatening injuries.
Diversions are in place.
Anyone with information on the crash should call 101, quoting incident number 181 of February 13.