An 85-year-old woman and her middle-aged daughter were murdered at their home at Laxmi Nagar in east Delhi on Sunday night.
Police said their throats had been slit. The murders were discovered by their domestic help early on Monday.
Ram Wati and her daughter Rajni Thakur, 55, were found dead at the one-storey home in Laxmi Nagar.
A property dispute may have led to the murder, police sources said.
Both women were widows and their only other relative was Thakur's daughter, who lives in Krishna Nagar.
"The police were informed around 9am. When policemen reached the house, they found a body lying on the bed and another on the floor," said a senior police officer who did not want to be named.
The police, who have not found any sign of struggle at the duo's home, suspect that a relative is involved in the murders.
"There is no sign of forceful entry. Things were scattered but that may have been done to misguide the police. But we are also probing whether robbers committed the murders," the officer added.
"It seems likely that property is the reason behind the killings," the officer said.
Forensic experts were called to collect evidence from the spot.
The women, who did not earn for a living, may have shouted for help but their voices were drowned out by the noise in the area.
"It seems Thakur resisted a bit but was overpowered. Two-three persons may have been involved in the murder," the official added.
The women spoke little to others in the area, their neighbours said. "Their family members would visit them often," a neighbour said.
* September 12, 2012: 70-year-old retd assistant commissioner of Income Tax department killed at Rohini house
* September 10, 2012: 58-year-old woman murdered in Lahori Gate
* September 5, 2012: 65-year-old woman strangled to death by robbers in Jyoti Nagar
* September 1, 2012: 55-year-old woman found gagged at Geeta colony house
* August 21, 2012: Former deputy director in I&B ministry and wife murdered in Shakarpur.