The staff were not attempting to manipulate a foreign exchange benchmark – an area being probed by regulators across the world.
Instead they manipulated a client’s order in the euro-zloty market.
It is understood that Commerzbank’s compliance procedures picked up the failed attempt to alter an order in January, and suspended the trader in February.
After an internal probe, another trader was suspended this month.
Now the German bank and regulators are deciding how to discipline those involved, which could end in their dismissal.
“Commerzbank has zero tolerance for non-compliance with rules and regulations,” said a spokesperson.
“We believe this incident was an isolated event and one from which the bank and the individuals concerned in no way profited.”