GARDAÍ have made a significant seizure of the recently banned head shop drug mephedrone in Ballymun – as detectives in north Dublin say they are increasingly concerned about the availability of the drug on the street.

Some 1.5kg of the drug, which has been given the nickname 'snow blow,' was seized by gardaí at a flat in Ballymun three weeks ago.

The drugs have an estimated value of more than €50,000. The substance is being analysed at the state laboratory. A man in his late 20s, a known local drug dealer, was arrested, but has not yet been charged.

Last week, gardaí in Coolock seized a smaller amount of the drug, which is also being analysed. Mephedrone-based drugs, which had been selling for between €15 and €30 per gram when they were legal, are now being sold for about €60 per gram – meaning dealers have increased the price of the drug by 100%.

A source said that mephedrone is increasingly available in north Dublin but the situation has not reached a serious point. One reason for the popularity of the substance is that it is still far cheaper to buy than cocaine and it has a dedicated following of recreational drug users since its popularity exploded in head shops earlier in the year.

"We are still dealing with people who have taken this substance and they are very difficult to deal with in custody," a source said. "They are anxious. Mephedrone can have a very negative effect on people's behaviour."

Gardaí and customs made the first significant seizure of mephedrone in July. A source said that dealers could be buying the drugs over the internet. The Psychoactive Substances Act, a blanket ban on all remaining legal highs, came into effect in August.

Any person caught selling products formerly known as 'legal highs' now faces prosecution and a jail term of up to five years.

In May, the government introduced new measures to criminalise the sale of several legal highs, including mephedrone. But immediately after this ban, a range of new products came on the market with a different chemical compound that was not covered by the ban.