US Federal Reserve chairman Ben Bernanke has told Congress that his colleagues at the New York Reserve Bank alerted British authorities to Libor issues in 2008.
He revealed the New York Reserve Bank sent recommendations to the British Bankers Association and also raised its concerns with the Bank of England.
He also said the Libor system, which sets inter-bank lending rates, is "structurally flawed",
Bernanke said he still did not have full confidence in the system
He told a Senate committee on Tuesday that it was not yet known whether any banks in the United States were involved in the rigging of Libor.
The Libor scandal erupted last month when Barclays was fined a total of around £290 million for trying to rig the Libor rate by mis-reporting the amount it cost them to borrow, sometimes working with other banks.