Shares of Danske bank tumbled on Friday, adding to an already sizable decline so far this year, following a Financial Times report which revealed that the bank - which has become embroiled in one of the largest money laundering scandals in European history - also executed "mirror trades" for Russian clients, raising the possibility that the bank is facing even more serious fines and sanctions.

Danske Bank executed up to €8.5 billion ($9.8 billion) in mirror trades for Russian customers in a single year, according to an internal memo cited by the FT. The memo raises "new insight into the scale and tactics behind its €200 billion money-laundering scandal." Deutsche Bank's Moscow desk also used mirror trades - wherein the same party takes both sides of a trade, selling in rubles then buying in dollars - to help criminals move money out of Russia, an activity for which it was fined more than $600 million. The bank earned some 10 million euros from the trades, it said.

Danske is already facing investigations in six countries, including the US, where the DOJ is investigating revelations of rampant money laundering through Danske's Estonian branch, which handled capital flows from non-resident clients that amount to multiples of the tiny Baltic nation's GDP.

The Danske memo, seen by the FT, estimated that Danske made €10m in 2013 from the mirror trades, which used Russian government bonds to allow customers to make international payments in a "faster, cheaper and more reliable way." "There is potential reputational risk in being seen to be assisting 'capital flight' from Russia," the memo said, before adding: “This is anyway a risk we run in other parts of our non-resident business, where the natural currency flow is always out of Russia. [ . . .] Given the strong income from the solution, the risk-return is seen as very attractive.”

Shares plunged 10% after the FT report to trade at their lowest level since 2014. And reports of a price-target downgrade from Credit Suisse certainly didn't help, as Reuters pointed out. CS cut the target to 199 Danish crowns ($30) from 244 crowns ($37).

"The investment case and key reason for buying Danske and taking anti-money-laundering risk is gone as buybacks no longer support shares," Credit Suisse said.

In an internal audit released last month, Danske revealed that upwards of $235 billion that flowed through the bank between 2008 and 2015 should be considered "suspect." CEO Thomas Borgen, who ran the bank's international division while the illict activity was taking place and pushed the bank to look the other way, has promised to resign as a result.

Meanwhile, Bloomberg reported that Danske Bank’s interim CFO Morten Mosegaard assured investors in an interview that there’s no risk of Danske being cut off from the US banking system as punishment for the banking scandal. But of course there's no way for Mosegaard to know for certain what the response from US authorities might be.

To be sure, the problem of money laundering in the Baltics isn't limited to Danske's Estonian operation. According to data from Estonia's central bank, as much as $1 trillion in non-resident money flowing through Estonian banks during that period should be considered suspect.

But Russian criminals and oligarchs who relied on these regulator loopholes can breath a sigh of relief. Because, as one compliance expert told Bloomberg, the Baltics aren't alone in having shoddy money laundering controls. Indeed, it's a European-wide problem.

"I’ve worked on AML in the Baltic states, and I haven’t seen anything worse there than I’ve seen elsewhere."

In other words, while Danske Bank is in the hot seat today, the game of regulatory whack-a-mole continues...