US authorities are closing in on banks and individuals they are investigating for the possible manipulation of the London Interbank Offered Rate – or Libor by issuing subpoenas to seven banks.

Reports say Deutsche Bank, Barclays, JPMorgan Chase, RBS, HSBC, UBS and Citigroup are the seven banks that have received subpoenas, which are related to the joint investigation by New York Attorney General Eric Schneiderman and Connecticut Attorney General George Jepsen.

Barclays was the first bank to settle with the US Department of Justice, the US Commodity Futures Trading Commission and the UK's Financial Services Authority for a record £290m for the manipulating Libor between 2005 and 2009.

Despite the record fine, the bank is still under investigation across different jurisdictions as well as from additional US regulators.

In addition - regulators from Tokyo to Toronto have revealed that they are investigating a significant number of banks that help set the benchmark interbank rates, which means there could be up to 43 banks under investigation in Europe alone.

Written and Presented by Lianna Brinded.