Rail services are expected to be cancelled, delayed or revised between London King’s Cross and Peterborough after a plastic balloon got caught in the overhead lines.
The balloon was wrapped around electric wires between London Kings Cross and Stevenage, meaning fewer trains are able to run on some lines.
The power supply has been switched off as a precaution while lines were inspected by Network Rail.
Specialist teams are now en route to the site and will need to block the line completely in order to safely remove the balloon.
One of the lines between the two stations is currently open to diesel trains.
Disruption is expected until at least 7.45pm.
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