The US Justice Department has charged 61 people in the alleged scam involving India-based call centres.
Twenty of these individuals were arrested in the US today, while 31 of these individuals and five call centers have been charged for their alleged involvement in the scam.
An additional US-based defendant is currently in the custody of immigration authorities.
Many of these, who were arrested in India recently, face deportation to the US.
The indictment alleges that the defendants were involved in a "sophisticated fraudulent scheme organised by conspirators in India, including a network of call centers in Ahmedabad", the Department of Justice said.
Using information obtained from data brokers and other sources, call-centre operators allegedly called potential victims while impersonating officials from the Internal Revenue Service or US Citizenship and Immigration Services.
According to the indictment, the call-centre operators then threatened potential victims with arrest, imprisonment, fines or deportation if they did not pay taxes or penalties to the government.
If the victims agreed to pay, the call-centres would then immediately turn to a network of US-based co-conspirators to liquidate and launder the extorted funds as quickly as possible by purchasing prepaid debit cards or through wire transfers, federal prosecutors alleged.
The prepaid debit cards were often registered using misappropriated personal identifying information of thousands of identity theft victims, and the wire transfers were directed by the criminal associates using fake names and fraudulent identifications, the indictment said.
According to the indictment, the co-conspirators allegedly used "hawalas" to direct the extorted funds to accounts belonging to US-based individuals. These individuals were expecting the hawala transfers but were not aware of the illicit nature of the funds. The co-conspirators also allegedly kept a percentage of the proceeds for themselves.
Mumbai Police unearthed the scam, involving more than Rs 500 crore, after raiding seven call centres on Mira Road. The con job had been going on for a few months, police have said.
The daily transactions of the call centres stood at around Rs 1.5 crore.
"This is a transnational problem, and demonstrates that modern criminals target Americans both from inside our borders and from abroad. Only by working tirelessly to gather evidence, build cases and working closely with foreign law enforcement partners to ensure there are no safe havens can we effectively address these threats," Assistant Attorney General Leslie R Caldwell told reporters at a news conference here.
(With inputs from PTI)