Twenty members of a gang, including 13 from Calcutta, involved in withdrawing money from bank accounts of US citizens, were sent to jail after their production in the court of chief judicial magistrate of Dhanbad on Sunday.

They were arrested on Saturday.

The arrested persons led by Saddam Ansari, son of a former councillor, and two former employees of a Calcutta-based call centre, Vikrant Singh, a resident of Kendua in Dhanbad, and Jwala Singh, a resident of Jorapokhar in Jharia, used to purchase data of clients from US companies.

At a news meet in his office on Sunday evening, Dhanbad senior superintendent of police Kishor Kaushal said: “The arrested persons were operating from a call centre-like set-up at Ena Islampur under the jurisdiction of Jharia police station, 5km from Dhanbad district headquarters. The centre has 44 central processing units (CPUs), 28 Internet protocol (IP) phones, eight modems, among other things.

“After purchasing client data such as mobile phone numbers, age and sex from US companies, the gang members, who operated as employees of Jain Edu Networks and Outlandish Pvt Ltd (names of companies they used as a front), used to drop voice messages using Internet Voice Response System. In the voice messages, they would say that ‘your bank account is likely to be closed because of insufficient balance’; or ‘money would be deducted from your account’. They also provided a toll-free number to their targets to ‘help them clarify doubts’,” said Kaushal.

He said when customers used to call on the toll-free number, the call got directed to an Internet protocol phone at the call centre.

While speaking to US citizens, the gang members also said that they had deposited money to avoid closure of their bank accounts but because of some glitch they had deposited extra money which the US citizen will have to refund after filling an online form.

“Using a software, the CPU of the American filling the online refund form, was hacked, and he could see extra money deposited in his bank. He then transferred the money back to the gang using gift cards or other mediums,” said Singh.

“We are in the process of investigation and some links are yet to be found as there are different layers in the scam. We will take the members of the gang into remand again to find out more details,” he said.

The gang was operating here for more than six months and its members claimed they carried out a fraud of $40000 (Rs 25 lakh). When asked if the gang used to target people of nations other than the US, the SSP said: “In the probe so far, we have found that the gang had targeted only US citizens.”