The deceased have been identified as Nishant, Balwinder and Laxman, who were friends and were involved in event-management business.
The bodies of three youths were found in a white-colour Honda City car (DL 4C AB 8076), owned by Balwinder, around 11 PM last night, they said.
Police suspect that the death might have happened due to the consumption of some poisonous substance or gas poisoning while chatting in a car.
"We have got to know that they were chatting inside the car with the AC on and eating some snacks. As per initial investigation, they might have died due to gas poisoning or consumption of poisonous substance as no injury marks have been found on their bodies. However, other angles are also being investigated," said a senior police officer.
"The post mortem report is being awaited to ascertain the exact cause of their death and further investigation is on," the officer added.
On the other hand, parents of the deceased are suspecting foul play in the incident and have alleged that they were given poisonous substance by someone.