The Delhi Police has questioned 20 relatives of the Burari-based family in connection with the mysterious deaths of its 11 members and is likely to rope in a psychiatrist to assist in the probe.
The police has ruled out the involvement of any godman.
The police recovered a third register with notes about 'salvation', 'shunya' and 'appeasing God'.
Policemen questioned 20 family members including the family matriarch's eldest son, her daughter and one of her deceased daughters-in-law's sisters, all of whom denied that the family indulged in 'occult', said a senior police officer.
Police has more or less ruled out the involvement of any self-styled godman in the case and are probing it as a case of 'shared psychosis'.
A senior officer also spoke to doctors from VIMHANS on Monday who also opined that it was a case of 'shared psychosis', in which one person's delusional beliefs are transmitted to others.
Meanwhile, the Crime Branch team again inspected the spot on Tuesday and found a register whose earliest entries were from 2011 and had psychological musings and notes about 'salvation', 'shunya' and 'appeasing God'.
They also spoke to the delivery boy, who was the last person to see them alive and who had delivered 20 rotis to the family on June 30, a day before they were found hanging.
10 of the 11 members of the Bhatia family were found hanging from an iron-mesh in the ceiling on Sunday, while the body of 77-year-old Narayan Devi, the head of the family, was lying on the floor in another room of the house.
Devi's daughter Pratibha, 57, her two sons Bhavnesh, 50, and Lalit Bhatia, 45, were also among the deceased. Bhavnesh's wife Savita, 48, and their three children -- Meenu, 23, Nidhi, 25, and Dhruv, aged 15, too were found dead.
Lalit Bhatia's wife Tina, 42, and their 15-year-old son Shivam were also among those found dead. Pratibha's daughter Priyanka, 33, who was engaged last month and would have married by the end of this year, was also found hanging.
The questioning of the family members began from 10 am today at the Burari police station.
A Crime Branch team, led by a Deputy Commissioner of Police-rank officer, on Monday questioned deceased Narayan Devi's eldest son, Dinesh, her daughter Sujata Nagpal, deceased Priyanka's fiance at the police station.
They also questioned Lalit's wife Tina's sisters since the investigation had revealed that Lalit and Tina were the ones, who had convinced the family about performing the rituals to attain 'salvation'.
Some neighbours were also questioned and some distant relatives who had attended Priyanka's engagement last month were also questioned.
Tina's three sisters, who stay in Rajasthan and Madhya Pradesh, also denied any such things and claimed that their brother-in-law and sister worshipped God like any other person and there was nothing that would point towards their involvement in 'occult' practices.
Lalit's elder brother Dinesh and sister Sujata were also questioned and they also maintained that the family was not into occult or did not follow any tantrik or godmen.
Priyanka's fiance, who was also questioned, said that she was a normal girl and had never mentioned about 'occult' practices.
He said that nothing in her behaviour indicated that she was thinking of committing suicide. Their was an arranged match and even when things were finalised, the Bhatia family had not carried out any rituals that would arouse suspicion, he told police.
He also said that Priyanka and he would talk often and would also discuss about their coming wedding.
These findings have led the police to believe that more than 'occult', this case is about the family's psyche.
The police suspect that the family might have been suffering from 'shared psychosis'.
"Shared psychosis means that delusional beliefs are transmitted from one person to another. In this case, it is suspected that Lalit Bhatia, 45, was the one who had the delusion of talking to his father even after his death. And his beliefs were endorsed by other family members too," he said.
They might rope in a psychiatrist to understand the psyche of the family.
Meanwhile, the family members have rejected the many theories as 'false and baseless'.
The family has claimed that there was no truth to any of such speculated theories and that the media was just trying to 'taint their image'.
The eldest daughter-in-law of the family told NDTV that they are being 'portrayed as a religious family involved in black magic'.
"If there was anything of this sort, I would have known it since I am the eldest daughter-in-law of the family. These are rumours. Everyone is connecting everything with 11 be it 11 pipes or 11 windows. All these are false. It is wrong," said Kamlesh, who has been living in Rajasthan with her family for 20 years.
Eleven pipes protruding out of a wall of the house fuelled rumours surround the deaths.
She said, "Instead of supporting the family, people are encouraging such rumours. I was here on June 11."
According to Kamlesh, she had attended the engagement ceremony of Priyanka. Kamlesh said everything was fine then.
Kamlesh's son Prashant too denied such rumours.
"As a family member, I would reject these rumours because we do not have any reason to believe it. We have been living here for long. We have never got a sign of any such activity," Prashant said.