Update, 4.30pm: British Transport Police are still working to remove the trespasser from the railway.
The line remains closed, however normal services are expected to resume at around 6pm.
East Midlands Trains has confirmed a trespassing incident near Grimsby has caused disruption on Grimsby/Lincoln/Leicester routes.
The incident occurred at Littlefield Lane Level Crossing and the line was closed as a result.
Network Rail and Humberside Police attended the scene and are working to reopen the line at the time of writing.
All trains along the route will terminate at Barnetby until further notice.
A replacement bus service is in place to run from Grimsby Town to Barnetby/Lincoln Central and Newark North Gate to Lincoln Central.