Police are searching for a trespasser who walked onto the track at Cross Gates station.
Officers from British Transport Police (BTP), West Yorkshire Police and the police helicopter have been trying to find the man who walked off the end of the platform at 1.36pm on Friday.
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A BTP spokesman said: "We are on the scene and conducting a thorough search of the railway with the support of the National Police Air Service.
"We have not located anybody and enquiries are ongoing."
Trains are running as normal.