A four-year-old girl and her grandmother (50) were found strangulated to death by an iron wire at their second floor flat in Pratap Vihar near NH 24 late on Wednesday.
The police said Sangita Mukherjee and her granddaughter Manyata were found dead around 8 p.m.
"Their mouths were found bandaged with a medical tape," SSP Raghubir Lal said.
He said the number of alleged killers is likely to be around three to four as four-five cups of tea were found on the table.
The police have rounded up one person as a suspect in the case and have also questioned a domestic help on suspicion.