Record quantities of former head shop drugs were stopped entering the country last year, with the seizure of several new substances.
Customs officers said the trade is increasing and that the products are being smuggled in by post, courier services, and the freight sector, mainly from China.
Officials made a number of massive seizures in controlled deliveries in joint operations with gardaí, including two linked operations resulting in the interception of 18kg of a cocktail of new drugs in Waterford last September.
While the supply and consumption of psychoactive substances in Ireland has fallen with the effective banning of former legal highs and the closure of head shops in 2010, many of the same powders and pills, and a range of new ones, are being supplied over the internet and sold illegally.
Details released to the Irish Examiner show more than 36kg of these psychoactive substances were seized entering the country in 2012.
*21kg of pyrovalerone, a stimulant powder not previously seized in Ireland before;
*8kg of 4-methylmethcathinone (4-Mec), another stimulant, also not seized before;
*5kg of methylone, a former head shop drug, seized previously in 2011;
*3kg of naphyrone, previously seen in head shop drugs, but this was the first time the drug was caught being illegally imported;
*11kg of ‘other psychoactive’ drugs, including synthetic smoking mixtures, similar to cannabis.
"Recent indications are that trade in these products is increasing in shipments of chemicals originating in China," said a Customs spokeswoman.
She said the drugs were often misleadingly described as chemicals with legitimate uses (bath salts, corrosion inhibitors, cleaning, or water treatment products).
"There is evidence of involvement of Irish citizens in importation, repackaging, and distribution (including re-exportation) of these products, but links to organised criminal groups have not been established to date," she said.
Drug researcher Tim Bingham said the large haul of 4-Mec might be a replacement for mephedrone, the hugely popular head shop drug. "4-Mec is known as mephedrone and might be replacing it," he said.
Mr Bingham said an interesting aspect of the seizures was the massive consignments of pyrovalorone, which was similar to ecstasy in effects and has also been found in mephedrone products.
He said there was a huge global trade in these products and said a lot was being supplied through hidden websites, including one called the Silk Road.
Mr Bingham said it was "very difficult" for Customs to intercept packages coming into the country over the internet: "I’ve spoken to a lot of people who have imported from Silk Road and only two or three ever had packages seized. Having said that there are more controlled deliveries, so law enforcement are more aware of it."