POLICE have warned that young people are playing Russian roulette with their lives by taking drugs which mimic the effect of cocaine and heroin after the death of a teenage girl.

Helen Henderson, 19, died after she was believed to have taken the Class B substance mephedrone, or MCAT - a former 'legal high' that was outlawed in 2010.

Ms Henderson fell ill at a flat in Renfrew, near Glasgow, on Sunday before being rushed to Paisley's Royal Alexandra Hospital where she died.

Police yesterday warned that such psychoactive substances (NPS) contain unknown chemicals with unpredictable and deadly effects.

They are being manufactured by chemists in labs as far afield as China and then imported to make pills and powders.

Detective Sergeant Michael Miller of the STOP (Statement of Opinion) Unit, based in Glasgow city centre, said officers face a constant battle against new drugs and toxic variations of known illegal substances.

He and his team are responsible for probing the use and distribution of these drugs and give expert evidence in court.

DS Miller said: "When someone dies and their death is linked to drugs, police will issue a health warning.

"I would like to stress that these warnings are not to be taken lightly. We mean it when we say that you are playing Russian roulette with your life if you take these or any drugs."

He said that drug manufacturers across the world are trying to "bypass the law" by altering the structure of drugs which are taken in clubs and at house parties in Glasgow and beyond.

He added: "These people might take cocaine or MDMA and add another substance to it to mimic the effect. This will never have been tested. No-one knows what this might do to their body."

It has emerged that medical staff are working blind to treat those who take the NPS, as they don't know what deadly chemicals they are dealing with.

They can only treat the symptoms of users, as toxic compounds attack their bodies often causing organs to shut down and fail.

DS Miller said the same threat is also posed by drugs sold as known illegal substances, as drug manufacturers strive to undercut each other in a competitive market and mix cheap chemicals into deadly tablets and pills.

These may be sold on as cocaine powder or ecstasy tablets, but their contents can never be trusted.

He added: "They are illegal for a reason. You never know exactly what you are taking and you cannot trust the person who is selling it to you - they might not know.

"The bottom line is that drug dealers are trying to make money. They are ruthless."