Gwent Police say they are working to establish what happened after a schoolbus left the road in the village of Llanfach this morning.
The schoolbus was carrying 20 children between 8 and 12 years old and three adults.
No injuries are reported. There have been no arrests and enquiries are ongoing. The road was closed while the bus was recovered.
Bus company Stagecoach says it will do all it can to assist police in their investigation.
More top news
Welsh Labour launches General Election campaign saying Ed Miliband in Downing Street would "deliver for Wales".
The motorist was kidnapped by the masked robber to act as his getaway driver - and he then tried to pay her £40 for giving him a lift.
Welsh Conservatives launch General Election campaign telling voters they are the only party with a "long term economic plan for Wales".