The bodies of a 60-year-old woman and her differently-abled daughter were found at their residence in outer Delhi's Mianwali Nagar area on Saturday morning, police said.
The deceased were identified as Shashi Talwar and her daughter Nidhi (40).
The incident came to light after their maid returned to work in the morning, the police said.
She rang the doorbell several times, but when there was no response, she entered the house from the other door and found the duo lying in a pool of blood, they said.
The maid informed the police at around 10 am, they added.
Shashi's throat was slit while Nidhi was attacked with a blunt object, the police said.
The police ruled out the robbery or theft angle in the case since the jewellery was found intact.
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Shashi's husband had died two years ago due to a heart attack.
Her two sons, Abhay and Vishal, live in Canada and Mumbai respectively.
Police is also scanning the footage of CCTV cameras installed in the nearby area to find clues.
They said Nidhi suffered from cerebral palsy due to which she did not have a regular schooling and stayed at home with her parents.
Police suspect that someone known to the family executed the killings since there were teacups lying in the drawing room.
Further investigation is underway, they said.