British Transport Police (BTP) is appealing for information after thieves attempted to steal cabling from railway track near Bargoed.
Officers are investigating after the cable was damaged between Pontlottyn and Rhymney on Saturday May 14.
Detective Inspector Mark Cleland, the officer leading the investigation, said: “The cable was severely damaged by the perpetrators of this attack, but fortunately it was not cut as it was armoured cable. Had it been cut, it could have had a major impact on the operational running of the railway.
“This sort of attack causes serious disruption to train services and the travelling public. The act of stealing cable is an extremely dangerous crime which is costly to the rail industry and to the thousands of passengers who rely on the rail network.
“I am now appealing for anyone who witnessed anything suspicious in the area, or who has any information regarding this incident, to contact us.”
The incident was reported to BTP at 11am on Saturday.
Mark Langman, route director for Network Rail, said: “These are serious criminal acts and they have to stop. Cable thieves have denied passengers the service they rightly expect and, through the massive cost to the industry, deny everyone improvements to rail services.
“We are doing everything we can to protect the railway and will continue to work closely with British Transport Police and other rail partners to do everything in our power to deter thieves and bring those who attack our network to justice.”
DI Cleland said additional measures were already being put in place in the area to tackle cable crime.
“We will be carrying out directed patrols throughout the Rhymney Valley and link with Gwent Police to gather intelligence on suspects in the area,” he added.
“Officers will also conduct regular visits to scrap metal dealers to roll out a code of conduct, and we’ll carry out leaflet drops in the area to highlight the issue.
“Cable theft is a major priority for BTP, and the Force will use all legally available powers to bring offenders to justice.”
Anyone with any information about cable theft should contact British Transport Police or Crimestoppers, where they can report the crime anonymously and could receive up to £1,000 reward if their information leads to a conviction.
Contact British Transport Police on 0800 40 50 40, quoting reference B8/WS of 17/05/2011, or call the independent charity Crimestoppers on 0800 555 111.