Delays to rail services going towards London are expected until 6pm after a woman was taken ill on a train at Letchworth.
An ambulance service spokesman said: "We are currently responding to reports of a woman taken ill on a train and have two ambulances attending at Letchworth Station."
Trains are unable to stop at platform one at the station.
Journeys through Letchworth towards London may be delayed by up to 20 minutes.
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 The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.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