The global probe into foreign exchange manipulation has widened to include 15 of the world's biggest banks and some of the most actively traded currencies, as lenders scramble to help authorities in exchange for leniency.
The UK's Financial Conduct Authority – one of seven regulators handling the worldwide investigation – has in so far requested information from at least 15 banks, according to two people close to the situation. The rapidly accelerating probe is looking at whether traders manipulated markets by sharing information and trading ahead of their clients.
(Read more: EU to fine banks billions of euros over rate rigging)
Investigations by the FCA as well as authorities in Switzerland, the US and Hong Kong are focusing on the euro-dollar market, the most liquid currency market in the world which accounts for almost a quarter of the $5.3 trillion daily trading volume.
Regulators and banks are also scrutinizing trading in sterling, Australian dollar and Scandinavian currencies, two people familiar with the situation said, pushing the probe well beyond the niche currency markets that were initially thought to be under review.