A 13-year-old Kaikohe boy had to be given emergency medical treatment following a seizure on Thursday which police believe may have been linked to smoking so-called synthetic cannabis.

The man-made drug has been blamed for several deaths around the country in recent weeks but serious reactions had not previously been publicly reported in Northland. Further details, including the teen's current condition, were not available at this stage.

So far the greatest problems seem to be in Auckland and Rotorua, where 20 people have been admitted to Rotorua Hospital's emergency department in the past 10 days after smoking the drug.