A top police officer said that laptops, desktop computers, notes and letters written by family members and diaries were recovered during the search this morning.
The letters, he said, were not sent by somebody but were surprisingly exchanged by the occupants of the flat between themselves.
"The letters were written just to communicate. In fact, some letters revealed that the writer was quite depressed, while another was probably in reply to those tried to console the writer," he said.
Arabindo De, the owner of the building, died in a fire inside a bathroom whose door was bolted from inside on Wednesday night.
More From This Section
The skeletons, purportedly of his 50-year-old daughter Debjani and their two pet dogs, were were found in the apartment the next day.
De's 45-year-old son and sole living family member, Partho, who has said that he was living with the skeletons for the past six months, has been found to be mentally unstable.
The skeletons of the pet dogs would also be tested, he said.
Police have also spoken to Arobindo's brother Arun, who lives next door, besides the security guard of the building.
"They (De family) had zero connection with the outside world. They had no maid and had severed connections with their relatives as well. But we are probing all possible angles in this case," he said.
Meanwhile, a medical team comprising three psychologists and two doctors has been formed to check on Partho's mental health.