The woman lived near Rana chowk along with her son and two daughters, Superintendent of Police (Rural area) Rajesh Pandey said.
The widow's sister-in-law and her son Anshul also lived in the same house. Last night, Anshul had gone out for work and when he returned home, he found his aunt and her three children lying unconscious in a pool of blood, he said.
Anshul told police that her aunt was lying naked on the bed with blood oozing out from her private parts.
Deputy Superintendent of Loni Anil Yadav said that there is no possibility of loot or any land dispute but rape could not be ruled out.
All the four were immediately rushed to GTB Hospital in east Delhi where doctors declared the woman and her son as brought dead. The condition of both the daughters is still critical and they are undergoing treatment.