Maryland and federal authorities announced Monday that they have shut down three Indian call centers linked to a gold bar scam that stole millions of dollars from American consumers.

Authorities said the operation netted almost $50 million from more than 600 victims across the U.S. through wire transfer, cryptocurrency and gold bar schemes. 

The six alleged leaders of the scheme were also arrested, authorities said. 

An ABC News investigation previously found that as the value of gold surged, grifters posing as federal agents convinced people — mostly older Americans — to convert their life savings into gold bars. 

As part of the scheme, scammers sent “couriers” to pick up the bars in person to allegedly keep them in a secure location.

Last year, ABC News interviewed a suspected courier from jail as he faced charges in two states for his alleged involvement in the scam. He claimed he was hired by an individual in India and paid between $800 and $4,000 per job to pick up packages, some of which contained gold bars.

John McCarthy, the Maryland state attorney for Montgomery County, announced Monday that his office had indicted 10 couriers accused of collecting money from victims, and said that several of those cases have already resulted in convictions.

“They’re targeting people who have retirement money, who have pensions, who have investments, who’ve maybe sold their homes and have that money in reserve,” McCarthy said.