The decomposed body of a 20-year-old woman and her two-year-old son was found at their rented house in outer Delhi's Swatantra Nagar, near Narela, on Tuesday evening.
Police suspect that the victims were killed by the man with whom the woman was living with at the house for the past 20 days.
The woman has been identified as Nisha. She lived with her son and one Santosh Kumar, a labourer, who used to claim that he was Nisha's husband. Police are trying to ascertain the permanent residential address of the victims, as their landlady had not got their credentials verified by the police.
According to a senior police officer, the incident came to light around 6.30 pm after the neighbours complained to the landlady about some foul smell emanating from the house.
"They saw the decomposed bodies of the victims when they peeped inside the room through a window. One of the neighbours called the police," the officer said.
The victims were taken to Babu Jagjivan Ram hospital where doctors said that the mother-son duo might have been strangled about five days ago. A case of murder has been registered at the Narela police station and efforts are on to nab Kumar.