The problem occurred at Risca & Pontymister station, affecting Transport for Wales services running between Cardiff Central and Ebbw Vale Town. Trains may be delayed by up to 20 minutes, and some services have been cancelled in both directions. Transport for Wales expects disruption to continue until 9am and has apologised for the inconvenience. A spokesperson for Transport for Wales said: "Due to a fault with the signalling system at Risca & Pontymister, services may be delayed by up to 20 minutes. "Services may be cancelled in both directions between Cardiff Central (CDF) and Ebbw Vale Town (EBB).