Detectives will examine how money laundering rules were followed at the bank's Danish subsidiary and could result in “sanctions”, Nordea said in a statement.
“We realize that we initially underestimated the complexity and the time it takes to change our procedures,” said Nordea chief executive Casper von Koskull.
The bank added that 850 Nordea employees are currently involved in the fight against money laundering which the bank plans to increase to 1,150 by the end of the year.
In May 2015 the bank was fined 50 million kronor (€5.4 million euros) – the maximum possible – by Swedish regulators who accused Nordea of “not following money laundering rules for several years” and failing to “evaluate the risks of (doing business with) certain clients”.