Wellington, March 18 NZPA - Quantities of a party drug linked to the death of two teenagers in Britain have been intercepted by New Zealand Customs officials, with police fearing a strong version of mephedrone is in use here as a substitute for ecstasy.

British police said mephedron contributed to the deaths of Louis Wainwright, 18, and Nicholas Smith, 19, who died on Monday, The Times in London reported.

Mephedron was rapidly gaining popularity in British schools and was now making inroads on the New Zealand party scene. It was legal in the UK but a banned Class C drug in New Zealand.

Customs officials have intercepted at least 15 packets of the drug -- 13 of them from Britain -- in the past four months.

The powdered form of the drug ostensibly sold as a plant fertiliser in Britain was being illegally imported, National Drugs Intelligence Bureau coordinator Detective Inspector Stuart Mills told NZPA.

The maximum penalty for its possession was three months jail and/or a $500 fine, with up to eight years in prison for importing or supplying.

"Concerns have been raised about the strength of mephedrone available in New Zealand and it is believed that some drug users take mephedrone as a substitute for ecstacy (MDMA)," he said.

"There is also a risk that tablets which people believe to be MDMA may in fact contain mephedrone."

Mephedrone is banned in Norway, Finland, Denmark, Israel and Sweden.

Mr Mills said police and the National Drugs Intelligence Bureau, were closely monitoring its supply and use here.

Potential side effects of the drug are reported to include fits, blood circulation problems, vomiting, nausea, nose bleeds, nose burns, hallucinations, rashes and paranoia.