The body found lying upside down in the drain was that of Sunanda Ganguly, who used to stay alone in the ground floor of an old two-storied building on Bakultala Road within Bhowanipore Police Station limits.
There was no injury marks on the woman's body but police said the way the body was lying upside down in the drain was "quite unnatural".
"Primary signs suggest it to be a case of murder. There are clear signs of struggle inside the room," Joint Commissioner of Kolkata Police of the Special Task Force (STF) Vishal Garg, who visited the murder site said.
Locals alleged that Ganguly was murdered by some promoters of the area who were eyeing the old building for a long time.
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Residents of the area also alleged that the promoters had allegedly kidnapped the old woman a couple of years back.
"The promoters were also trying to prove her as insane. They were after her for a long time because she was reluctant to vacate the room of the building which was sold to them by the owner. She was threatened by the promoters and complaints were lodged at Bhowanipore Police Station regarding this though no action was initiated," a local resident said.
Sniffer dogs, sleuths from the Kolkata Police homicide department have started investigation into the matter.