Network Rail says a landslip that caused a train to derail near Bargoed today arose as a result of flooding and snow thaw over the weekend.
We are relieved that no-one was injured in this incident and that passengers were able to quickly resume their journeys.
However, it could be some time before the line fully reopens. The train has to be moved, and that will depend on any damage to it or the tracks.
"The tracks will then have to be inspected and any repairs carried out. It is too early to say how long that will take.
More top news
Will the 'potentially historic' snow storm hitting the US, find its way to the UK?
A young mother from Haverfordwest is warning others not to send explicit pictures or video after she became a victim of 'revenge porn'.
Thicker cloud across the northwest will tend to spread southeastwards through the day