Five youths including three girls were coming from Shahbaad side in the car after attending a birthday party, they said.
When they were crossing near Kuldeep Nagar, their car rammed into they truck, police said.
All the occupants of the car sustained serious injuries. They were rushed to local civil hospital at Ambala Cantt where four of them were declared brought dead, they said.
The deceased have been identified as Anshika Jain, Ridhima, Deepak Bansal, Sunny Aahluwalia while one of the injured was referred to PGIMER, Chandigarh.
Health Minister Anil Vij reached at Civil hospital and condoled the guardian of the deceased.