Thieves caused commuter chaos on the Rhymney Valley line on Tuesday morning after they stole railway cabling.
Three-hundred metres of cabling was stolen from track near Gilfach Fargoed train station causing signal failure.
A British Transport Police (BTP) spokesman said: “Officers are currently investigating the theft of railway cable from a section of track near Gilfach Fargoed railway station.
“The incident was reported to BTP at 5.48am on Tuesday March 20 following a report of signalling failure in the area.
“Officers attended the incident alongside engineers from Network Rail and it was discovered that a total of 300 metres of cable had been stolen.
“Patrols are currently being conducted and enquiries are ongoing. Crime scene investigators are on site and visits are also being made to scrap metal dealers, who are assisting officers with their enquiries.”
Caerphilly’s Labour AM Jeff Cuthbert condemned the theft and said: “This despicable and potentially life threatening theft caused massive inconvenience to commuters and other rail passengers on the Rhymney Valley line.”
Anyone with information, or who saw any suspicious activity in the area, is urged to contact BTP on 0800 40 50 40, quoting log reference 46 of 20/03/2012.