New York's leading financial regulator, Benjamin Lawsky, the financial services superintendent, has demanded documents from a dozen banks to investigate the manipulation of currency positions and market.
Barclays, Goldman Sachs, RBS and Deutsche are among those under investigation into trading practices in the foreign exchange market.
A source in Lawsky’s office said the investigation is currently at an early stage.
“We are investigating a broad range of concerns about foreign exchange trading at these institutions,” said the source, who asked not to be identified.
Reuters revealed on Tuesday that Deutsche Bank had fired three New York-based currency traders amid signs of a widening investigation.
Citigroup, JP Morgan and others have also confirmed they are in the process of co-operating with the investigation.
The investigation is the latest in a list of regulators and law enforcement offices around the world that are looking into whether traders at the largest banks unduly influenced currency fixes, front-run large customer orders and engaged in other manipulative practices.
By Tony Aynsley