Two people who are familiar with the probe, who declined to be named due to the private nature of the discussions, noted that the European Commission sent requests to banks to figure out how the rates are calculated, Bloomberg reports.
Guillaume Prache - managing director of EuroInvestors - said: "It's very good news that the commission is eventually digging its nose into these money-market behaviors."
The news agency added that Barclays, which is the third-largest bank by assets in the UK, is currently talking to British and US regulators over the Libor investigations.
Last week, the Wall Street Journal reported that a number of Barclays' shareholders had voiced dismay at a pay report that will see chief executive of the lender Bob Diamond receiving a Â£6.5 million ($10.7 million) bonus.
By Claire Archer