According to the police, the woman, a native of Madhubani district in Bihar, and her four-year-old son were strangled using a cloth.
Mohammad Salman, who was a friend of the deceased woman, is one of the suspect in the case as he is missing since the crime came to light, they said.
The woman had separated from her husband three years ago and was residing here with her son at her sister's house, police said, adding she later moved into a rented 'jhuggi' with Salman.
They were rushed to a nearby hospital but were declared brought dead by the doctors, the official said, adding that a murder case was lodged at the Sarai Rohilla police station.
Efforts are on to apprehend Salman, a native of Varanasi in Uttar Pradesh, as he was living with the victim since past few weeks, police said.
"Prima facie, it appears that Salman first strangled the woman and then killed her son while they were asleep," the officer said.
