Four members of a family were found killed at their Mayur Vihar colony residence on the Hambran road, the police said on Tuesday.
However, Rajiv Sood, the owner of the house and a property dealer, was not found at home, they added.
A sharp-edged weapon was used to kill Mr Sood's wife Sunita, son Ashish, daughter-in-law Garima and a 13-year-old grandson, senior police official Sameer Verma said.
The incident came to light when Garima's father came to visit his daughter. When nobody opened the door, he informed the neighbours and the police.
The police did not rule out the possibility of a family dispute behind the incident.
They also found Sood's car from a spot near the South City locality. The vehicle was found burnt though nobody was inside it, the police said.
The bodies will be sent for post-mortem, they said, adding that a case has been lodged and a probe is on.