Six of them were on board the trunk, which was proceeding towards Puducherry carrying empty tins and the incident happened at Edaiyur Kuppam village.
A car coming from behind rammed the truck and in the impact, the truck overturned, while the car plunged into a pit off the road. Fellow motorists and passersby rushed the victims to Chengalpattu Government Hospital.
On information, Mahabalipuram police rushed to the spot and cleared the vehicles to resume traffic on the stretch. A case has been registered and further investigation is on.