A neighbour was the first to discover the bodies. When he entered the house, he saw the bodies of four men and seven women in the courtyard of the two-storey house in Sant Nagar in Burari area. The dead included three teenagers.

"Some of them were found hanging from an iron grill ceiling (used as a ventilator) in the courtyard while others were lying on the floor blindfolded with their hands and legs tied," Joint Commissioner of Police Rajesh Khurana said.

"Prima facie, we suspect they committed suicide but we are also investigating the case with other possible angles of homicide. We are not ruling out anything. We are also checking the CCTV footages."

Khurana said no suicide note was found. The horrific scene of a middle aged man and a woman as well as two boys and a girl hanging from the ceiling went viral on the social media. Their mouths were gagged with pieces of clothes and four them were blinfodled.

The bodies were sent for post mortem to ascertain the cause of deaths.

Of the victims, there were two brothers: Bhupinder, a grocery store owner, and Lalit Singh, who ran a plywood store.

"Their shop would open by 6 a.m. every morning but when it did not till 7.30 a.m. today, a neighbour went to buy milk. Upon checking, the neighbour found the main door of their residence open, prompting him to inform the police," Khurana said.

A neighbour who refused to believe that it was a case of mass suicide said Lalit and Bhupinder were very friendly persons.

"I spoke to Bhupinder last night. He was very happy and there was no sign of any stress."

Chief Minister Arvind Kejriwal visited Burari.

"It is a tragic incident. I have spoken to the police. Let's wait for their investigation to be over," Kejriwal told reporters.