According to the latest update from Network Rail, 8 passengers and 2 crew members were on board the train that derailed near Bargoed this morning.
There were 3 reported minor injuries, which were treated at the scene.
The emergency services and Network Rail are on site dealing with the incident.
Trains on the Rhymney Valley line are starting and terminating at Bargoed, with a bus service running between Bargoed and Rhymney.
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There is likely to be a good deal of cloud around today, thickest in the southeast, where outbreaks of rain are possible at times.
A dry night with clear spells for most, especially towards the north where it will become rather chilly with some mist patches possible.
Wales head coach Warren Gatland says some players suffered a few bumps and bruises during their clash against Ireland.