Five Asian nationals were last night being questioned at three separate garda stations over an alleged "invoice redirection" fraud valued at almost €500,000, which targeted at Dublin Zoo.
The three men and two women, aged between 20s and 60s, were also being quizzed about a similar theft of more than €250,000, which happened at an education company that services Co Meath and Co Louth.
Invoice redirection fraud happens when a business is contacted by someone pretending to be from a trusted supplier or a service provider saying that their bank details have changed.
The victim then unwittingly sends any payments due to this new account and the thieves withdraw the cash.
The five people arrested in dawn swoops yesterday are all suspected of being part of an organised crime network and originally from the Indian subcontinent. In the case of Dublin Zoo, the organisation was hit on three separate occasions last October and November.
The highest figure taken from the zoo was €310,000, but this money was frozen in a bank account after a detailed probe by specialist fraud investigators.
No Dublin Zoo customer was compromised as part of the elaborate crime.
However, the fraudsters are suspected of obtaining €76,000 and €75,000 in other transactions from the zoo.
These amounts have not been recovered by gardai.
In a similar case, which happened around the same time Dublin Zoo was scammed, the money laundering gang is suspected of obtaining €250,000 from an educational business, whose base is in Dundalk.
On that occasion, the criminal gang posed as a construction company.
This money has not yet been recovered as gardai are working on tracing it.
Investigators from the Garda National Economic Crime Bureau (GNECB) swooped on three properties in Tipperary and one in Dublin after launching a huge money-laundering investigation.
Computers, mobile phones and other electronic devices were seized.
"The GNECB, assisted by the Cyber Crime Unit and gardai from Tipperary and Blanchardstown, carried out four searches - three in Tipperary and one in Dublin - and have arrested five people," a garda spokesman said.
He added that they were detained at Clonmel, Cahir and Tallaght garda stations, under the provisions of Section 4 of the Criminal Justice Act 1984 as amended.