GARDAÍ have seized seven tonnes of drugs from eight "production factories" manufacturing a range of former 'legal highs,' the Sunday Tribune has learned.

The massive haul, worth tens of millions of euros, was seized by gardaí in a series of raids of factories in Dublin and Cork on 12 May.

Only a small proportion of the drugs was seized from the country's 102 head shops; the majority were handed over voluntarily when detectives from the garda national drugs unit (GNDU), supported by local units, raided eight production factories where many of the people involved in the sale and supply of legal highs were manufacturing the products.

One of these factories was in Dublin's Baldonnell and run by Englishmen; another was in Harold's Cross, while another was operating in Tallaght under the direction of an Australian.

A Polish national was running another one of the premises in Dublin and all of his products were being exported to Poland. Another factory was in Cork and largely served the market in the south.

Up until recently and before a range of legal highs were banned on 11 May, those involved in the trade were importing the products from abroad and then using premises as "distribution factories" to sort the drugs into thousands of "separate deals" in plastic bags.

But those involved in the trade soon realised the kind of money that could be made and many of these eight premises had turned into "wholesale manufacturing factories", according to a source.

When gardaí visited the eight premises, they found people using mixing agents to produce a range of legal highs. In one of the raids, gardaí discovered the floor covered with imitation cannabis leaves that were being sprayed with a substance by people wearing protective masks.

The biggest seizure was from the factory in Tallaght, where gardaí confiscated one tonne of drugs.

"The sheer volume of what's been seized is astonishing and it shows how popular legal highs had become in Ireland compared with the sale of cocaine," said a source. "It's also significant that the people involved in the trade in Ireland had moved away from simply importing it but were actually manufacturing it."

As part of Operation Kingfisher, gardaí visited all 102 head shops and eight production factories within 24 hours of the sudden ban on 11 May.

Those involved in the trade were told that specified drugs were now illegal and were requested to surrender them voluntarily, which they did.

The ban prohibited a long list of drugs, including nearly all cannabis-type smoking blends along with a range of powders, such as hugely popular mephedrone, and party pills.

The ban is soon to be extended . The Criminal Justice (Psychoactive Substances) Bill 2010, which will outlaw the sale of all psychotropic substances, has passed all stages of the Oireachtas and is expected to be signed by the president soon.