A fallen tree caught on the overhead electric wires between Grantham and Newark North Gate is causing train delays.
Part of the tree has caused damage to the wires, meaning the train line is blocked and services are unable to run through the area.
Delays are expected to last until 4pm while the situation is resolved by Network Rail engineers.
Commuters from London Kings Cross can use their ticket to travel on Avanti West Coast services to Manchester Piccadilly and change for Transpennine Express services to Leeds and York.
Customers from Leeds or York can use their tickets to travel vice versa to Kings Cross customers.
People travelling between Stevenage or Peterborough and London Kings Cross can use their tickets to travel on Great Northern services in both directions.
To see which journeys have been affected by the delays, click here.