Swiss bank UBS approached US authorities in September with information relating to an industry-wide probe into alleged rigging of currency markets, in the hope of gaining antitrust immunity if charged with wrongdoing, sources said.

UBS is seeking to take advantage of a programme from the US justice department’s antitrust division under which the first company to report misconduct relating to a cartel can earn immunity from antitrust charges if it co-operates and provides information about other members of the group, three sources said.

Following the Libor interest-rate rigging scandal that has so far cost banks around the world $6 billion in fines and settlements, UBS sought to act quickly to gather and supply information when similar allegations of wrongdoing by leading banks in foreign exchange surfaced in June, the sources said.

No bank or individual has been accused of any wrongdoing but banks, including UBS, have said they are cooperating with regulators in the investigations. It is not known whether they too have sought first-mover advantage under the department’s programme.

UBS declined comment beyond pointing to a passage in its third-quarter results released in October, saying that after the June report of irregularities in forex markets, it had started an internal review.

"UBS and other financial institutions have received requests from various authorities relating to their foreign exchange businesses and UBS is cooperating with the authorities," the bank said in its results statement. Authorities including the US department of justice (DoJ), Britain's Financial Conduct Authority (FCA) and watchdogs in Germany and Switzerland are probing allegations of collusion between senior traders at big banks to manipulate benchmark currency rates.

These exchange rates or “fixes” are used to price trillions of dollars worth of investments and deals and are relied on by companies, investors and central banks globally.

Stung by Libor, banks are looking to cooperate more readily with regulators probing the FX allegations, which FCA chief Martin Wheatley has said are "every bit as bad as Libor".

Banks have put on leave, suspended or fired more than 20 traders in an attempt to show regulators they are cooperating and taking action.

UBS, which received leniency from some US authorities for its role in rigging Libor benchmark interest rates because of the information it supplied, scrambled to compile information on currency trading and get it to the DoJ early, the people said.

The move was “a huge gamble” according to one source, since it was handing over information with no guarantee that it would benefit from a programme that rewards the first firm to cooperate in a cartel probe with immunity from prosecution.

Although UBS paid $1.5 billion in 2012 to US and European authorities over alleged efforts to manipulate Libor and other benchmark interest rates - the largest such penalty to date - it did not face antitrust charges, which could have substantially added to its penalties.

It was unclear whether the strategy will work in the FX case as well. The sources said US authorities have given little sign so far of their intentions. The DoJ declined comment.

The forex investigation centres on groups of traders at big banks including UBS who are alleged to have shared on Bloomberg chatrooms - with names such as "The Cartel" and "The Bandits' Club" - market-sensitive information surrounding the benchmark rate known as the 4 o'clock London fix.

After media reports of alleged forex market manipulation surfaced in the summer of 2013, UBS went into “high gear”, hiring lawyers Gibson Dunn & Crutcher who within 10 days unearthed potentially incriminating chats by traders, the first source said.

US regulatory officials then visited UBS shortly after to search for evidence, the sources said. Having already co-operated with the DoJ on Libor, there was a debate within the bank about how much to reveal about what it had discovered on FX, the source said.

Then on September 14th UBS called the DoJ to say something had been discovered, the sources said. UBS could not at that stage disclose what that something was, but would be reporting it 14 days later to the DoJ.

The sources did not give any detail about what had been discovered. Several sources familiar with the FX investigation have told Reuters banks were rattled by Libor so were inclined to cooperate much more readily with authorities when the FX scandal emerged, to take advantage of “leniency programmes”.