A synthetic drug that is up to five times as powerful as cannabis is being sold legally in Britain, as incense.
It has already been made illegal in Germany and is also banned in the Netherlands.
The drug is based on the chemical JWH018 which mimics the effects of tetra hydra cannabol or THC, the main active ingredient of cannabis.
Drugs watchdogs are currently investigating the sale of the substance in the UK.
JWH018, was first synthesised in a US lab in 1995. It was originally developed for scientific experiments on chemical receptors in the brain.
However, it is now being manufactured in China, and is being sold at UK events like rock festivals as part of the growing "legal high" industry.
The UK drugs regulator, the Medicine and Healthcare products Regulatory Agency (MHRA), is understood to have identified JWH018 in products available in the UK. It is currently in order to determine whether or not it should be classified as a medicinal product - which would mean it should only be available from a doctor.
The UK Advisory Council on the Misuse of Drugs, which advises the government on whether a drug should be made illegal, is also aware of the substance, and is investigating it.
In addition to being illegal in Germany, it has been banned in the Netherlands and its legality is under review in Austria.
But scientists do not know what side effects the drug could have, as no tests have been done on its toxicity either in the lab or on animals.
Toxicologist Dr John Ramsey, who runs the Tic Tac Communications drugs database at St George's Medical School in London, said: "It's not a problem at the moment, in that we're not aware of casualties appearing in A&E, but there's an underlying potential for a problem."
He added that there were between 20 and 30 other similar substances that could be added to the incense mixtures.
Source - http://news.bbc.co.uk/1/hi/health/7887720.stm