They said the driver of the car, coming from Ramnagar near Bengaluru, applied brakes to avoid a dog.
This resulted in the vehicle swerving and hitting a parapet wall and turn turtle before hitting four persons, including a woman, near Chenjeri on Palladam-Udumalpet Road, about 35 Kms from here.
The passersby managed to pull out those in the car and also under it and informed the police and ambulance, who rushed to the spot, they said.
Four others, accompanying the ill-fated car and going to Munnar for tour, also sustained injuries as their car also swerved after applying brakes. They were also treated as outpatients in a private hospital, police said.