A top Deutsche Bank salesperson was placed on leave last month after the German bank found what it regarded as inappropriate communication between her and Singapore's central bank, according to a person familiar with the matter, marking a significant new twist in the multipronged, yearlong global investigation into the currencies market.

Kai Lew, a director of sales at Deutsche Bank in London tasked with handling central-bank clients, was put on leave because the bank-the biggest currencies dealer in the world-concluded that she had improperly shared trading information with the Monetary Authority of Singapore, or MAS, this person said. She is one of roughly 30 employees at nine banks who have been fired or suspended as part of a burgeoning global investigation into possible manipulation of currencies markets, and the first in sales rather than trading. At the time her suspension was first reported, March 31, the reasons for the move were unclear.