The Financial Times said that US state prosecutors have sent subpoenas to Bank of America, Bank of Tokyo Mitsubishi UFJ, Credit Suisse, Lloyds Banking Group, Rabobank, Royal Bank of Canada, Société Générale, Norinchukin Bank and West LB.
New York attorney-general Eric Schneiderman and Connecticut attorney-general George Jepsen are attempting to determine whether the institutions participated in schemes to manipulate the lending gauge, a source told the newspaper.
They join Deutsche Bank, Citigroup, JPMorgan Chase, Royal Bank of Scotland, Barclays, HSBC and UBS in the investigation and increase the number of banks under examination by the two prosecutors to 16.
Schneiderman and Jepsen’s probe follows a number of separate investigations being run on three continents by prosecutors and regulators in countries such as the UK, Canada, Japan and the US.
Unlike US federal prosecutors, the New York attorney-general wields his state’s Martin Act, which allows a prosecutor to bring charges against anyone doing business in the state without needed to show they intended to commit fraud.
The Libor-rigging scandal was brought to public attention in June when Barclays agreed to pay about $450m (£279.3m) to authorities in the UK and the US to settle claims that it had tried to manipulate the lending rate.