Trains into Preston were delayed on Sunday evening after a cat was electrocuted when it climbed into a signal box, say Network Rail.
The cat, which is believed to have been a stray, climbed into the box on one of the coldest nights of the year.
Network Rail are now investigating how the animal was able to get inside the box.
A network rail spokesperson said: "At 7pm on Sunday, December 10, we responded to a small fire at our signal box in Preston, which was caused by a stray cat that had found its way into the unit.
"Sadly the cat climbed on top of a 650v transformer and did not survive.
"The damage to the signal box has now been fixed and we are investigating how the cat was able to get inside."
Trains are believed to have been disrupted for around an hour while engineers dealt with the issue.