Welwyn Garden City train station (Image: Charlotte McLaughlin)
A person has been hit by a train between London Kings Cross/Moorgate and Stevenage.
The tragedy occurred earlier this morning, and the emergency services are reportedly present at an incident near Twentieth Mile Bridge at WGC.
All lines have reopened but trains may be cancelled or delayed by up to 90 minutes until approximately 17:30.
Great Northern Rail tweeted: "Avoid travelling via Welwyn Garden City until later today if possible. If you must travel on this route, you will be required to use alternative transport and your journey will take longer than usual."
The police and ambulance service have been contacted for more information.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here