Officers say the suspects obtained lists of US tax defaulters and used threats to obtain their bank details.
The scam is said to have netted more than $150,000 (£118,000) a day, making it one of the biggest frauds in India's history.
Thane police officials said they were contacting the FBI to ask for help.
Some 70 of those detained were formally arrested, police said, with the rest released pending further inquiries. Nine people believed to have led the scam have been identified.
