Three people were arrested in raids carried out in June that involved both the specialist economic crimes department of the State Police and the no-nonsense Omega tactical unit.
Criminal proceedings have been launched over large-scale money-laundering after officers discovered an apparent "shell bank" - an illegal credit institution operating outside the jurisdiction of its place of registered business.
Shell banks are typically used to perform parallel or off-the-books transactions for money-laundering or tax evasion purposes.
Police have not revealed the name of the bank concerned or the identities of those arrested, other than to say that all three are foreign nationals.
That raises the likelihood that the operation may have been geared towards serving clients in Russia or other former CIS countries.
After years of denying the laundering of suspect cash from the east was a problem in Latvia, over the last twelve months the authorities have begun to clamp down after a series of major scandals suggested it was in fact a significant problem after all.
The shell bank was operating in Riga since at least January 2014, in rented office space and is suspected of legalizing the proceeds of crime on a large scale with daily transactions amounting to millions of euros.
Companies in Latvian, Estonia, Poland, Russia and other countries were used, as well as a number of current accounts with various credit institutions.
The volume of payments, which was carried out on a daily basis at the "shell bank", amounted to several million euros.