British police and investigators arrested three men on Tuesday on suspicion of manipulating the interbank lending rate Libor, the Serious Fraud Office said.
"Three men, aged 33, 41 and 47, have been arrested and taken to a London police station for interview in connection with the investigation into the manipulation of Libor," said an SFO statement.
All three men are British nationals, the SFO said. Two were arrested in Essex to the east of London and another was held in Surrey to the south of the capital.
The SFO opened a probe into Libor manipulation in July after Barclays was fined £290 million (359 million euros, $467 million) by US and UK regulators for rigging the key lending rate.
The London Interbank Offered Rate (Libor) is a flagship instrument used all over the world, affecting what banks, businesses and homeowners pay to borrow money.
A number of traders at Barclays were found to have rigged Libor to boost profits and bonus rewards, while the bank was also accused of lowering submissions to alter the perception of the lender's finances.
The claims ultimately led to the resignation of Barclays boss Bob Diamond and sparked a bitter row over ethics in the banking sector.
Other banks are being investigated by the SFO, the government department responsible for investigating and prosecuting complex fraud.
There was no immediate indication of which bank was involved in Tuesday's arrests.