The charred bodies of five members of a family, including one with injury marks, were found from a house that caught fire early Monday, police said.
A blood stained bedsheet was also recovered from the house in the city's Regent Park area, police said.
"The house was locked from inside and after we broke in we found five badly charred bodies. All the dead are members of the same family. One of the bodies has an injury mark. The bodies have been sent for post-mortem examination," Joint Commissioner of Police (crime) PK Ghosh said.
Ghosh refused to comment on the cause of deaths and said: "The probe is on and we are exploring all avenues."
The fire service was alerted by the neighbours after they heard a loud explosion and saw flames leaping out of the building.
"At around 2.15 a.m., we heard a loud explosion and saw flames leaping out of the third floor where the deceased lived. We alerted the fire brigade which later discovered the charred bodies," said a neighbour.
Eyewitnesses said they did not hear any screams or shouts for help.
"The bodies along with that of a dog were recovered from the same room. All of them were badly charred. However, there were no signs of struggle inside the house to suggest they sought help during the incident," a fire services official said.