U.S. CFTC refers alleged rate-rigging to Justice Dept -report

WASHINGTON, Sept 8 (Reuters) - The top U.S. derivatives regulator has referred evidence of potential criminal manipulation of a key benchmark known as "ISDAfix" to the Justice Department for possible prosecution, Bloomberg reported on Monday.

The Commodity Futures Trading Commission has been investigating possible manipulation of ISDAfix since November 2012, when it first sent subpoenas to many of the world's largest banks.

Bloomberg's story on Monday was sourced to a person familiar with the matter.

ISDAfix is an important reference point used to set benchmark rates for financial swaps products.

The rates are based on a survey from a panel of banks using a range of different currencies.

The United Kingdom-based inter-dealer broker ICAP Plc (LSE: IAP.L - news) was previously responsible for collecting the data from the banks, but it lost that responsibility amid the CFTC's probe. Thomson Reuters Corp took over the role earlier this year.

ISDAfix is one of several key benchmarks to come under scrutiny by civil and criminal investigators over concerns about manipulation.

In addition to U.S. authorities, the United Kingdom's Financial Conduct Authority is also involved in investigating possible manipulation of ISADfix.

Spokesmen for the CFTC and Justice Department declined to comment about the story. (Reporting by Sarah N Lynch. Editing by Andre Grenon)