A bus carrying 40 primary school-aged pupils home from a trip to the French Alps has plunged down a wooded slope into a creek, leaving the driver and his partner hospitalised with serious injuries.
Eighteen children and one other adult were treated for minor injuries, mayor of the town of Corps said Fabien Mulyk, where the incident happened said.
All of the children were said to be taken and four were taken to be looked over in hospital.
Local officials told French media that weather conditions were clear when the bus left the road, and no ice or snow on the section where the bus vehicle crashed.
They said all the children were wearing seat belts.
The mayor said the "most probable scenario" is that the driver had some kind of medical problem while behind the wheel.
A photo from the town published online showed the bus leaning off the slope of a ravine in a tangle of dried branches with its windshield shattered.
According to local media, the children in the vehicle were returning from a summer camp in the Hautes-Alpes.
They were heading towards Grenoble station, in order to then return to the town of Sceaux, in Hauts-de-Seine, where they are from.
The Route Napoléon, is a very steep national road linking Grenoble to Gap.
It is reported to be known for its dangerousness, with frequent fatal road accidents, including one in July 2007 which claimed the lives of 26 Polish pilgrims.