The four persons, all residents of Delhi, were on their way from Nangal to Najafgarh (in Delhi), they said.
The mishap occurred when the car bearing a Haryana registration number lost control and hit a safety wall of the bridge, Station House Officer, Satish Kumar said.
The local residents pulled out the injured and shifted them to Civil Hospital at Anandpur Sahib.
The doctors declared four of them as brought dead while the condition of the fifth one was stated as serious, police said, adding a case has been registered in this connection.