Police were called to a crash in Market Rasen after a car and a motorcycle collided on Caistor Road.
It happened this afternoon (Sunday, August 7) at about 4.40pm.
Two people have been seriously injured and taken to hospital, a spokesman for the force confirmed.
It is believed a black Seat Toledo and a black Honda motor cycle are the vehicles involved.
Anyone who was in the area at the time and saw either the car or the motorcycle before the collision or saw the collision itself is asked to contact police on 101 or the witness hotline on 01522 558855.