Services are currently running at a reduced speed through Welwyn Garden City following trespassers being reported in the area.
Commuters are advised to use their normal route, but expect an additional 15 minutes onto their journey time.
This is affecting Thameslink and Great Northern services through this station and onto journeys between London and Stevenage.
Disruption is expected until 4.45pm.
For more information visit: greatnorthernrail.com/travel-information/plan-your-journey/service-updates.
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 The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.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