An international fraud and cyber crime cartel, some of whom are based in Ireland, controlled more than 300 bank accounts in Ireland and has stolen at least €15 million, gardai believe.
After a Garda investigation into the money laundering section of the west African cartel, a team of over 100 gardai raided addresses across five counties on Thursday from 7am.
While the senior officers leading the inquiry are certain at least €14.6 million has been stolen and laundered to date, the true figure may be very significantly higher.
Gardai will not know how much cash has been stolen and how much of that is spent or recoverable until some 350 bank accounts in Ireland that have now been frozen are examined.
Financial documents
The Garda has gone to the courts to secure orders to block any further activity on some of the accounts. In other cases banks in Ireland moved to block accounts based on the information supplied by the Garda.
There are further accounts located in France, Italy, China, Nigeria and elsewhere.
The people targeted in the Republic in Thursday's raids are from Nigeria. Fifteen premises across Dublin, Louth, Meath, Kildare and Laois are being searched as part of the operation.
A large quantity of financial documents along with laptops and other electronic devices were seized. These will now be examined for evidence. Gardai also seized four 4X4 vehicles on suspicion of being the proceeds of crime.
Some of the people targeted were claiming unemployment and other social welfare benefits while living in rented houses paid for by the State.
The inquiry is being led by Det Supt Alf Martin of the Garda National Economic Crime Bureau, assisted by personnel from the Northern, Eastern and Dublin Metropolitan regions, along with officers from the drugs and organised crime unit, and armed support units.
Invoice redirect fraud
Gardai believe they are part of a wide network of west Africans engaged in invoice redirect fraud globally.
And it appears much of the money stolen by fraudsters all over the world was sent to the cartel members based in Ireland so they could launder it.
Some of the money was transferred between many bank accounts internationally, including China and west Africa, in the hope that no police force could track and find it to seize.
With some of the other money, expensive goods were bought and shipped out of the country. They were then sold at their destination country and effectively converted back into cash.
Invoice redirect fraud involves criminals setting up fake online identities to enable them pose as a legitimate trading company. They then contact the customers of the company they are impersonating and advise them of a change of bank account details.
If the scam works, the next time a payment is due to the company they are impersonating the sum will be paid into the new bank account, which is controlled by the criminals.
Once the money has been lodged into the criminals account, it can take days for the victims to realise what has happened.
The company paying out the money will have no way of knowing they have lodged a fee for goods or services to the wrong. Typically they will only realise when the company who was supposed to receive the payment sends a reminder after the payment appears delayed.
Some of the individual frauds have involved very large amounts of money. In February it emerged more than €750,000 was stolen, mostly from Dublin Zoo and Meath Education and Training Board.