An On Track Machine has failed and subsequently, the rescue resource (unknown) has become derailed at Panteg where I think it could been in process of crossing over. All lines closed and attempting to source Road Transport. Passengers advised to travel other routes, i.e. Birmingham, in meantime. Lines cannot be re-opened until Emergency services and RAIB have completed investigations, ETA 1800. Stressed no passenger trains involved. Originaly only Down Line affected but now all closed.