LONDON (AP) — Trillions of dollars change hands every day in the global foreign-exchange markets. Major currencies like dollars, euros and yen are traded in a scantly regulated market dominated by a group of elite banks.

Regulators in the U.S., Britain and Switzerland are accusing several international banks of conspiring to manipulate the rates for exchanging currencies. They announced Wednesday a total of $3.4 billion in fines against Citibank, JPMorgan Chase, HSBC, Royal Bank of Scotland and UBS.

WHAT HAPPENED?

Regulators in the U.S. and Europe found that the banks had failed to adequately train and supervise foreign currency traders. As a result, traders were able to form groups that shared information and sought to manipulate the market.

WHY IS IT IMPORTANT?

The scandal could become even bigger than the one surrounding the rigging of the London interbank offered rate, or LIBOR, which resulted in billions in fines for the banks implicated. Experts say that because the forex probe goes to the integrity of the markets, rather than just a single rate, it could have greater repercussions.

Jeffrey Bergstrand, University of Notre Dame finance professor and former Federal Reserve economist, says it is possible the case will result in tougher regulations for the markets — but that it would have to be coordinated internationally.

"The foreign exchange market is going to be difficult because it is so diffuse," he said "The boundaries are the market itself."

WHO GOT INVOLVED?

The Swiss Financial Market Supervisory Authority, the U.S. Commodity Futures Trading Commission, and the U.K. Financial Conduct Authority levied the fines announced Wednesday.

The U.S. Department of Justice, the U.K. Serious Fraud Office, Swiss Competition Commission and the Hong Kong Monetary Authority are also investigating.

Citigroup Inc. cited a $600 million charge and JPMorgan Chase & Co. about $400 million. The three British also set aside millions.

WHO KNEW AND WHEN?

Regulators found that the manipulation occurred between Jan. 1, 2008 and Oct. 15, 2013.

The scandal touched the Bank of England earlier this year, when it suspended an employee and launched a sweeping investigation that examined 15,000 emails, 21,000 Bloomberg and Reuters chat room records and 40 hours of telephone recordings.

Results of the Bank of England's investigation released Wednesday showed that the bank's chief foreign currency dealer was aware that bank traders were sharing information from at least May 16, 2008. From at least Nov. 28, 2012, he had concerns this could involve "collusive behavior," but failed to inform his superiors. This was "an error of judgment," but the chief dealer was not involved in any unlawful behavior, the investigation found.