A woman and teenage boy are in hospital with serious injuries after their car went over a 12-metre embankment in Cape Breton.

Police and emergency crews responded to the single-vehicle collision on Frenchvale Road, southwest of North Sydney, shortly after 7 p.m. Thursday.

Investigators say the car left the road, went over the embankment and travelled about 24 metres before coming to a stop in the woods.

The 28-year-old female driver was trapped inside while her 13-year-old nephew was thrown from the vehicle.  

Firefighters from North Sydney and Frenchvale used the Jaws of Life to free the woman from the car.

The boy and his aunt were taken to the Cape Breton Regional Hospital in Sydney with serious injuries.

Police say they are investigating the crash but it appears speed may have been a factor.