Two sources told Bloomberg that foreign exchange traders have been invited by the UK Financial Conduct Authority or FCA as the investigation on currency rigging continues. The people spoke on the condition of anonymity since the information was confidential. The US markets regulator had invited traders in the past weeks to voluntarily talk about the investigation. One of the sources said the regulators has looked into the communications of at least 40 traders, which include those recently called for interviews. FCA spokesman Chris Hamilton did not comment on the report.

According to a Bloomberg report, regulators from the US, UK, Switzerland and Asia were conducting investigations of alleged rate-rigging in the foreign exchange market, which has a daily value of USD 5.3 trillion. In June, Bloomberg News reported that the dealers attempted to rig the WM/Reuters benchmark rate by conspiring with counterparts. The report said the dealers pushed through trades before and through the one-minute windows when the benchmarks were established.

As the probe widens, around 11 lenders have said that regulators had gotten in touch with them. They include the Goldman Sachs Group Barclays and Goldman Sachs Group Inc. Bloomberg also reported that at least 12 traders were already suspended.

Meanwhile, several banks also confirmed that they have undertaken their own internal reviews about the matter. One of these was the Royal Bank of Scotland Group. Chief Executive Officer Ross McEwan said in a news conference held this month, "We will come down very severely on anyone who we discover is breaking the rules." A source also told Bloomberg earlier this month that RBS had issued a suspension of two foreign exchange traders based in London as a result of its internal investigation. The source added that RBS had given the communications of one of its former senior traders to regulators.