All lines are blocked on train services running between Leeds and York, CrossCountry said.
The disruption is being caused by a lightning strike on a signalling system based in York, according to initial reports.
"DISRUPTION: Due to lightning damaging the signalling system between Leeds and York all lines are blocked.
"Train services running through these stations will be delayed through the area."
Delays are also affecting services in Sheffield and Doncaster.
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