Three young adults have suffered severe kidney injuries this month after smoking synthetic cannabinoids, the Canterbury District Health Board says.
Two required treatment in intensive care.
In 2011 the Government banned all existing synthetic cannabis products, including industry-leader Kronic, which had been sold in dairies.
However, new products have skirted the ban by having a slightly altered chemical make-up.
Canterbury medical officer of health Alistair Humphrey said clinicians had growing concerns about the easy accessibility and safety of the drugs, as well as the long term effects they could have on people's physical and mental health.