A crackdown in the US has resulted so far in the seizure of 37 rhino horns, which authorities there have valued at between $8m (€6m) and $10m (€7.7m).
Operation Crash has not to date arrested any members of the so-called Rathkeale Rovers, a criminal Traveller network, originally from Rathkeale in Co Limerick.
The Rathkeale Rovers have become notorious across Europe and beyond for their involvement in the highly profitable rhino horn trade.
Last July, the EU police agency, Europol, said the Traveller gang was an “organised crime group” which was also heavily involved in tarmac fraud, the distribution of counterfeit goods, organised robbery, money laundering and drug trafficking.
It said their reach spread across North and South America, China and Australia and that they used “intimidation and violence” in their activities.
Europol estimate that rhino horns, which are used in traditional medicine and decoration, were worth between €25,000 and €200,000 each.
The agency said the Irish gang sourced horns by targeting antique dealers, auction houses, art galleries, museums, private collections and zoos.
It said they sold them by “exploiting” international auction houses in France, the US and China.
Europol said the gang had invested “significant proceeds of crime in Ireland — mainly in real estate and other assets”.
Rhino horn is sold in Chinese traditional medicine, as an aphrodisiac, as a decoration or to produce luxury products.
Trading in rhino horns is illegal under UN laws as they are an endangered species.
Last February, three agencies in the US — the US Fish and Wildlife Service, the Homeland Security Department and the Internal Revenue Service — set up a huge operation to uncover buyers of rhino horn.
Edward Grace of the US Fish and Wildlife Service said 37 rhino horns were seized in the country’s biggest ever operation in this area.
Among eight people arrested were a rodeo cowboy, a Chinese businessman, a Vietnamese nail salon owner and a US antiques expert.
Though no Irish people were arrested in the crackdown, more arrests are expected in the coming months, Mr Grace said.
“This case also involves other Irish buying rhino horns in the US,” Mr Grace told AFP. “I can’t go into a lot of details on it.”
He said criminals scoured the country for trophies of the animals hunted illegally in South Africa and brought back in the US in recent decades.
It was the activities of two Irish men, Richard O’Brien and Michael Hegarty, from Rathkeale, Co Limerick, that brought the attention of US law enforcement to the trade.
The duo were arrested after paying undercover agents in Colorado some $17,000 for four black rhino horns.
They told agents they planned to hide them in furniture which they would ship to Ireland.
They were charged with conspiracy, smuggling and money laundering, and served six months in a US prison.
Mr Grace said the trade in illegal rhino horn was “really being fuelled by the Irish Travellers”, but said Chinese and Vietnamese criminals were also involved.
He likened the crime to the drugs trade: “It is similar to an operation of a drug cartel. You have the higher ups who provide the money, the mid-level lieutenants who get the couriers and the smugglers, so you have the whole organised criminal element here.”
In the United States, it is illegal to sell most types of rhino horns across state lines and none may be imported or exported without a special permit.
The maximum penalties are a $250,000 fine and five years in prison for conspiracy and trafficking of endangered species, and $100,000 and one year in prison for violating the Endangered Species Act.
Since illegal trafficking fuels poaching of endangered rhinos abroad, “part of the responsibility worldwide to help protect these species falls on the United States,” said Mr Grace.