"If a product is labelled 'not for human consumption' then do not smoke it -- if it is smoked, it should not be sold to people under the age of 18."
Senior Sergeant Jason McCoy, of Oamaru, said police were also investigating its sale for any legislation breaches.
Oamaru police identified the product as "Firebird". It is advertised as "the ultimate in aromatherapy", and a 3 gram packet was yesterday selling for $18 at Super Save, in Oamaru.
Super Save closed its doors following the ban on psychoactive products, a sign on the door stating it was closed "until further notice". However, it recently re-opened.
A salesman said the packet of Firebird, bought by the Otago Daily Times yesterday, was the last in stock -- it had been very popular.
The ingredients are not listed, and it is described as a "proprietary blend of exotic South American and Southeast Asian herbs, herbal extracts, essential oils, natural flavour and fragrances designed to stimulate the mind and body when burned in an appropriate environment".
While it is described as non-toxic in nature, not containing any illegal or restricted substances, it is an R18 product and "not intended for human consumption".
Snr Sgt McCoy said legal highs were an underlying cause of most crimes in Oamaru for a long time, by people either offending under the influence, or offending to fund the addiction.
But since the ban in May crime had fallen.
"It is a concern that people have substituted [burning incense] for [legal highs]," he said.
"But we're yet to deal with the extreme [effects]."
National Poisons Centre toxicologist Dr Leo Schep, of Dunedin, said those who chose to smoke burning incense did so at their own risk.
"When you smoke it, you don't know what it's been changed into ... we don't know what happens when people smoke it," Dr Schep said.
There would likely be an increased risk of respiratory problems in the long-term, but he did not anticipate it would have any "extreme" effects.
However, with no specific ingredients listed, it was possible people could have allergic reactions.
"Probably, it's going to do nothing for you - it's just another attempt to sell plant matter," he said. "[But] you don't know."
Since the use, sale and manufacture of the products were made illegal in May, the number of calls to the National Poisons Centre had reduced dramatically - from about 70 in April, to no more than eight in the last month, Dr Schep said.
Waitaki Mayor Gary Kircher said the resurfacing of products in Oamaru highlighted the difficulty of legislating and banning them.
"I remain adamant that we don't need this rubbish in our town and district," Mr Kircher said.
A New Zealand website, Bona, with the slogan "be organically naturally aware", was selling five sachets, plus one free, for $100.
The website says it contains "no illegal, banned or restrictive substances such as cannabinoids, not legal highs".
When the Otago Daily Times called the contact phone number listed on the site, the man who answered refused to give his name, saying: "I just run the bloody website".
He denied the incense was a replacement for legal highs and said it was "just incense".
It was made in Kaiapoi, in Canterbury. He said it had been passed by the Canterbury Employers Chamber of Commerce.
However, chamber chief executive Peter Townsend said the chamber did not approve products, and to say the product had been passed by the chamber was "just extraordinary".
"That's just so off the mark," he said. "First of all we don't pass anything _ it's not our role."
The Kaiapoi company packaging the incense was not a chamber member. "Our good reputation is being impugned here," he said.
