Delays were caused between Preston and Blackburn after a person under a train at Lostock Hall.
British Transport Police were called to a stretch of line between Bamber Bridge and Lostock Hall at Farrington Curve around 5.15pm on Monday,
Reports indicated a person was “stuck under a train”.
Transport Police confirmed the woman, aged in her 40s, was taken to hospital and was still alive but suffering from major head injuries.
Police arrested a man whose train was stuck at a signal after the incident.
In a tweet the police said the man was “raging” about the incident and the delays. He was given a £90 on the spot fine.
Northern Rail said delays of around two hours were being experienced up until 7pm.