Thieves stole 60 metres of railway cabling between Pontlottyn and Rhymney causing delays for commuters on Thursday morning.
A British Transport Police (BTP) spokesman said:
“BTP officers were called to a section of track near Rhymney railway station at 6.10am today (Thursday, May 31) following reports of signalling problems in the area.
“After conducting a search of the area, it was discovered that 60 metres of signalling cable had been stolen from near Sebastopol Bridge, between Ponlottyn and Rhymney.
“Patrols are currently being conducted, crime scene investigators are on site and enquiries are ongoing.
“The incident has caused disruption to passengers and the rail network, with services between Bargoed and Rhymney delayed.”