The incident happened at around 01:15 am when the truck, coming from Dhaula Kuan, hit the railing on ring road near the All India Institute of Medical Sciences (AIIMS) and crossed over to the other side, they said.
Five cars were damaged and three persons sustained minor injuries.
The truck driver managed to escape and a manhunt has been launched after a case was registered on the complaint of one of the injured, Mohan Gupta.
Mr Gupta was discharged after treatment, while another person, Kishor is undergoing treatment at the hospital and is said to be out of danger, police said.
It is suspected that the truck was being driven at a high speed and the driver lost control over the vehicle, the police said.