The city police’s detective department is investigating if an organised gang is at work across Calcutta and neighbouring areas cheating people by promising them hefty returns from bitcoin investments.

The investigation comes in the wake of the arrest of Sujan Rakshit from his office in Hazra on Friday. Rakshit was arrested for cheating Sayantan Bhanja of Rs 1.28 crore by making him invest in bitcoins, police said.

In his complaint with the police, Bhanja has alleged that between January 2017 and March 2018 he had invested Rs 1.52 crore in Rakshit’s firm.

He has said that Rakshit paid him Rs 24.22 lakh as returns from the investment to gain his trust. Of this amount Rakshit had returned Rs 3.5 lakh in two months in 2018.

When the returns stopped from April 2018, Bhanja visited Rakshit’s Hazra office and found it to always locked, he has said in the complaint.

He filed the complaint in December 2019 and the detective department’s special cell started investigating the matter.

A team of officers froze two of Rakshit’s bank accounts in two private banks. But he remained untraceable. On Friday, officers learnt he had returned to his Hazra office. A team raided the office and arrested him.

Rakshit has pleaded ignorance and said he has been framed. A city court has sent him to police custody till August 19, an officer said.

“Bhanja had met Rakshit in the Baghajatin area in 2016. He had introduced himself to Bhanja as the CEO of an investment company,” a detective department officer said. “Bhanja was then looking for avenues to invest in order to expand his business.”

In the course of the next few meetings, Rakshit told Bhanja about bitcoins. One of his executives even followed up the matter with Bhanja.

Bhanja ended up paying Rs 1.52 crore, the police said. When he realised he had been cheated, he filed the complaint.

In April, singer Anupam Roy had lodged a complaint with the police alleging he had received a mail where the sender claimed to have accessed his personal data and demanded payment in bitcoins to let go his personal data.

The same month, two professionals, who were working from home and using an app to make video calls, had received ransomware threats demanding payment in bitcoins, an officer said. The complainants had said they received a specific link in their mails to buy bitcoins, the officer said.