NEW DELHI, July 3 (Xinhua) -- Mystery around the deaths of 11 members of an extended family in the Indian capital Delhi seems to be deepening with every passing day.

As police officials investigating the case see it as a case of "mass suicide linked to spiritual and mystical practices", the family members reject the police theory and demand a thorough probe into what they view as "murder".

On Sunday morning 11 members of Bhatia family were found dead inside their house in Burari, of north Delhi. While bodies of 10 members of the family were found hanging from the ceiling in the hallway of their home, the family elder 75-year-old Narayan Devi's body was lying on the floor.

The dead include Devi's daughter, two sons, their wives, and five grandchildren aged between 33 and 15 years.

Police officials say those found hanging had hands tied behind their backs, and their eyes and mouths covered with cloth.

The Bhatia family owned a three-storey house and ran two shops on its ground floor -- one sold plywood and the other groceries.

Police officials say the oldest grandchild, 33-year-old Priyanka (one among the dead) working at an IT company was engaged two weeks ago.

Police officials say they did not came across any sign of forced entry into the house. Reports said the gold jewellery and mobile phones were untouched.

Police officials say they have found handwritten notes -- "a diary", which they believe refer to "unusual practices and beliefs" that might have prompted the family for a mass suicide as part of a "spiritual practice."

However, surviving members of the family reject the police theory and deny having seen any diary.

The members blame media for "labelling their family as maniacs".

"People saying ours was a deeply religious family and believed in magic is totally wrong," Kamlesh Chundawat, daughter-in-law of the family said. "Has this been the case, I being the eldest daughter-in-law would have known about it."

As police struggles to resolve the case between a "mass murder" to "mass suicide", the mystery shrouding the deaths has sent shockwaves across India.