Two persons were being questioned in connection with the incident which took place yesterday, the sources said.
While one of the two is a lady attendant for 84-year old Gouri Bhattacharya, who was one of those killed, the other was a youth.
The youth, who was reportedly like a son to the attendant, used to take her to work everyday, the sources said.
The woman had reported sick yesterday and another lady attendant, who was on night shift, worked in her place. This attendant was also murdered.
While bodies of Gouri Bhattacharya and her son Dipak (52) were discovered in a room in the first floor, that of domestic help Anima Das (48) was found lying in the dining hall of ground floor and the attendant in the bathroom of the house on Biren Roy Road (west), near Sakher Bazar.
All the bodies had deep gashes on throat.
The sleuths were also exploring the possibility of any family feud behind the murders, believed to have taken place between 8.30-9.30 pm with TV on in the first floor room.