A slew of global currency traders at some of the world's biggest banks have been put on leave in recent days amid an escalating probe into potential manipulation of the $5 trillion-a-day global foreign-exchange markets.

More than 10 traders at five major currency-dealing banks are now on a leave of absence in connection with the global investigation into the clubby world of top currency traders. This swath of departures leaves some big gaps among the market's chief so-called "risk takers" who place short-term bets in order to provide prices to the rest of the market.