Police have issued a warning after a man died moments after smoking a legal high.
The 38-year-old victim smoked a herbal incense called Psyclone, shortly before his death.
The product is sold legally in the UK and can be bought online for £7.99.
The victim died shortly after smoking the drug while visiting a friend's home last Sunday in Bolton, Greater Manchester.
His cause of death has not yet been established but Greater Manchester Police (GMP) said there are no suspicious circumstances.
A number of other people detectives have spoken to as part of the investigation also admitted smoking the legal high.
Detective Sergeant Rob Parker from GMP said: "We do not yet know how the man died but we are of course working with the coroner to establish the full circumstances.
"Worryingly we know the man and others he was with had smoked herbal incense.
"The sole purpose is to use it as a legal high and faced with what we know we feel it is incumbent upon us to send out what will appear to most to be an extremely obvious safety message.
"Put simply, do not smoke herbal incense. It is not for direct inhalation and you do not know what effect it will have on your well-being."
The market for such legal highs has grown in the past decade with a multitude of substances now on sale online or in high-street "head shops".
Many of the products, including Psyclone, carrying warnings telling users it is not for human consumption.
Harry Shapiro, director of communications at national charity Drugscope, said there was a "cat and mouse" situation between the producers and dealers of such legal highs and the authorities trying to stop their use.
"It is a legal conundrum," he said.
"What they are is synthetic cannabinoids. They are chemicals, they are not made from cannabis, they are laboratory made substances that act on the brain the same way cannabis does."
But Mr Shapiro said despite some of the products being legal users will not really know what they are taking.
"It's as much a lottery as anything else you are taking, you are taking on trust what you are buying, whether in a head shop or online or round the back of a club," he added.
"The only advice on all of this is no drug equals no risk, but people will experiment and try things."