The global probe into foreign exchange manipulation has widened to include 15 of the 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 sprawling investigation, has requested information from at least 15 banks, according to two people close to the situation. The accelerating probe is looking at whether traders manipulated markets by sharing information and trading ahead of clients.

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 $5.3tn daily trading volume – pushing the probe well beyond the niche markets that were thought to be under review.