VANDALS brought the railway network around Meadowhall to a standstill by placing cable across the tracks.
Two passenger trains suffered damaged undercarriages after striking the cabling at Ecclesfield on Sunday, November 19.
Northern Rail has put forward a £500 reward for any information about the incident which leads to a conviction.
Sergeant Andy Selby, of British Transport Police, said: “As we’ve witnessed from this incident, cable theft has a huge impact on the railway network and leads to lengthy and disruptive journeys to passengers.”
Northern Rail head of trains and stations Chris Jackson said: “It’s truly unbelievable that people will do anything as mindless as this.
“It’s only through good fortune that no-one was injured as a result of this senseless vandalism.
“We are committed to working with our colleagues at BTP to trace those responsible and are offering £500 to anyone with information which leads to a conviction.”
Network Rail community safety manager Vickie Beadle added: “This type of behaviour is incredibly dangerous and people need to realise that the railway is not a playground.
“This incident is completely unacceptable and caused unnecessary disruption for those simply trying to get home.”
Text 61016 or call 0800 405040 quoting reference 514 of November 19. Alternatively, ring Crimestoppers anonymously on 0800 555 111.