Commerzbank has suspended two traders under suspicion of having tried to manipulate the Polish zloty's euro exchange rate in regular trading, the bank said on Wednesday.
Their departure comes a day after Germany's financial watchdog Bafin said it had clear evidence that market participants attempted to influence reference currency rates and widened an investigation to include many more banks.
Worldwide investigations of currency markets and reference rates show banks are still struggling to control the behavior of some traders even after the regulatory pressure that followed the financial crisis.
At least one of the two suspended traders was based in Commerzbank's Frankfurt headquarters. The global investigations have focused mostly on London, the world's biggest currency trading center.
"We believe this incident was an isolated event and one from which the bank and the individuals concerned in no way profited," Commerzbank said in a statement.
The attempted manipulation took place in January and one of the traders was suspended in February, a spokesman for the bank said. Following an internal probe, a second trader was suspended in May, the spokesman said.
The bank has discovered no evidence of any other attempts at the bank to manipulate currency prices, he said. Internal controls had identified the attempted manipulation, the spokesman added.
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A Bafin spokesman was not immediately available for comment.
Authorities in the United States, Britain, Switzerland, Germany and Singapore are examining whether traders from different banks worked together to influence currency prices, but also whether they traded ahead of their own customers or failed to accurately represent to customers how they were determining the prices.
Regulators are looking at how traders deal with several key benchmarks, from interest rates to foreign exchange and commodities. Eight financial firms have been fined billions of dollars for manipulating reference interest rates, and the probe into the largely unregulated $5.3 trillion-a-day foreign exchange market could prove even costlier.
More than 30 foreign exchange traders worldwide have been suspended as part of the probes.
Commerzbank's local rival Deutsche Bank,, the world's largest forex trading bank, has suspended several currency traders in North and South America.