The victims belonged to the same family and most of them had lived in the same home in Burari village in the northern part of New Delhi, said police officer Vineet Kumar.
Police are investigating whether the victims four men, three women and four girls died by suicide or were killed, Kumar said, adding that no suicide note was found.
There were no bullet marks on the bodies of the victims, and there was no sign of forced entry into the house, Kumar said.
Ten bodies, blindfolded by cotton and pieces of cloth, were found hanging from an iron grill used as a ventilator in the home's courtyard, while the body of a 70-year-old woman was lying on the floor of the house, said a police official who spoke on condition of anonymity, in line with department policy.
The family had been living in the house for more than two decades, the Hindustan Times reported.
It also said that the house belongs to a businessman who ran a plywood shop and dairy.
The newspaper said that at around 8am on Sunday, a neighbour with whom the businessman used to go for morning walks went to see him and found the door of the house open and 10 people — including the businessman — hanging. He raised an alarm and people from the neighbourhood called the police.
“It is a tragic incident. Police are investigating it. Let's wait for their investigation to be over,” said New Delhi Chief Minister Arvind Kejriwal, who visited the scene.
In a video posted on Twitter by Kejriwal's ruling party, the neighbours are heard telling Kejriwal that the family was busy with wedding preparations.
A neighbour of the family said they couldn't have committed suicide, New Delhi Television reported.
According to the report, the neighbour said he spoke to one of the victims on Saturday night and found no sign of any stress.
Indian TV channels broadcasted interviews with neighbours who said the family did not have any discord among themselves.
Police official Rajesh Khurana told reporters that all angles were being investigated. “We can't rule out anything,” he said.
