A 42-year-old woman in Alipore received a phone call saying it was from the Telecom Regulatory Authority of India and that her mobile number was about to be blocked because they had come across a phone number issued in her name that had an FIR drawn by Mumbai police against it.

Scared, the woman logged into Shype, as told, and was “interrogated” for hours at a stretch over three days on video call by men in uniform who said they were from Mumbai police. At the end of the “interrogation”, the fraudster succeeded in extracting ₹31 lakh from her.

The “cops” threatened to arrest her in a ₹500-crore money laundering case, for which the owner of Jet Airways, Naresh Goyal, had been arrested by the Enforcement Directorate earlier this year.

The conmen — one of whom pretended to be an IPS officer — managed to make the woman, who works as a nursing officer at a hospital in Alipore, transfer ₹31 lakh in multiple instalments after promising her that the “arrest warrant issued against her by a court” would be withheld if she paid her entire savings to a “secret account”, which she did.

Officers at the Kolkata Police headquarters said such complaints were rampant. Many Calcuttans, they said, were receiving phone calls from unknown numbers. The callers pretend to be cops and force their targets to shell hefty amounts with the threat of arrest.

“As part of the modus operandi, the fraudsters are first instilling a deep sense of fear in their victims by convincing them that they will be arrested if they did not cooperate with the ‘investigation’,” said an officer at Lalbazar.

In this case, the woman became convinced after the fraudsters correctly mentioned her Aadhaar number that she had been implicated in the money laundering case.

“The next step is to talk to the victims for hours through video calls and convince them that their family will be in danger if the person mentions the conversation to anyone. During the conversation, the fraudsters try to extract details of the person’s bank accounts and how much money they have in them,” said the officer.

In this case, the woman was also asked to report to Mumbai police immediately but when she said she had recently undergone surgery in her leg, she was asked to share her bank details and the funds she had in each of them.

The woman was made to transfer ₹31 lakh to four bank accounts and was told that she would get back the money soon, police said.

“As the woman pleaded innocence and promised to cooperate, she was told that she and her family were in danger and that she should send the Mumbai police a 30-second video clip of her every few hours as proof that she was all right,” said an officer of the cyber cell of the south division of Kolkata Police.

The woman was given receipts for each of the transactions she made to win her trust. The police said the receipts turned out to be fake.

An officer at Lalbazar said they have been receiving such complaints for a few months. In many similar cases that have been reported to Kolkata Police, the victims had been asked to leave home and check into a hotel so they would not be influenced by others.

The police said they are investigating the complaint lodged by the Alipore woman.