Societe Generale, Royal Bank of Canada, and Bank of America are among nine additional banks subpoenaed in a multistate investigation of alleged manipulation of Libor, according to a person familiar with the matter.

The subpoenas, issued by New York Attorney General Eric Schneiderman starting in August, bring to 16 the number of banks subpoenaed in the states' investigation, said the person, who asked not to be identified because there wasn't authorization to speak publicly.

Schneiderman and Connecticut Attorney General George Jepsen have been jointly investigating claims that banks rigged the London interbank offered rate, or Libor, a worldwide benchmark for borrowing. The same person said in August that seven banks were subpoenaed in their investigation, including JPMorgan Chase & Co. and Barclays Plc.

The probe is now "a large, well-coordinated multistate investigation that includes attorneys general throughout the U.S.," Jaclyn Falkowski, a spokeswoman for the Connecticut attorney general, said today in an e-mailed statement.

"A primary focus of the multistate investigation is to identify whether state and municipal issuers with financial instruments pegged to Libor and other benchmark interest rates have been harmed by the alleged conduct and, if so, to seek recovery of those taxpayer funds," Falkowski said, declining further comment.

Florida Attorney General Pam Bondi has also issued subpoenas to more than a dozen financial institutions, including UBS, Deutsche Bank and HSBC.

Besides Societe Generale, Royal Bank of Canada and Bank of America, the other six banks to receive subpoenas from New York are: Credit Suisse, Bank of Tokyo Mitsubishi, Norinchukin Bank, Rabobank, Lloyd, and West LB, a German lender that ceased operations.

Representatives of those banks couldn't be reached for comment or declined to comment on the subpoenas.

Lloyd's has said it's assisting various regulators in their investigations into the setting of Libor. Royal Bank of Canada has said it's cooperating with regulators and found no evidence of collusion with other banks.

Rabobank said in a report this year that it received subpoenas and requests for information from regulatory agencies in the U.S., Europe and Asia and is cooperating.

Melissa Grace, a spokeswoman for Schneiderman, declined to comment on the investigation.

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