Emergency crews have been dealing with the incident on the line between Doncaster and Gainsborough Lea Road stations this morning.
Details of the incident have not been released.
A spokesman for National Rail said that Grand Central services between Bradford Interchange and London Kings Cross, Hull Trains services between Hull and London Kings Cross and LNER services between Aberdeen / Newcastle / Leeds / Bradford Forster Square and London Kings Cross were all being disrupted.
Although the line has now re-opened, passengers have been warned of delays and cancellations.
A spokesman said: “Following the emergency services dealing with an incident between Doncaster and Gainsborough Lea Road, all lines have reopened.
“Services between Doncaster and Peterborough are being diverted on this route as a result of planned engineering work, and therefore trains between these stations have been disrupted. Trains may be delayed or cancelled while services return to normal.”