A teenager has died after taking fake ecstasy tablets the seventh reported death linked to the pills.
Police say the tablets circulating in Scotland contain toxic chemicals with potentially fatal effects.
The latest case saw an 18-year-old woman die in Alexandria, West Dunbartonshire, on Tuesday morning.
Three male friends aged 18, 21 and 25 were admitted to the Royal Alexandra Hospital. Doctors are still treating the 25-year-old.
Police in the west of Scotland have identified the pills as green and stamped with a crown logo and say some have been found to contain a dangerous stimulant Methoxyamphetamine, known as PMA.
They are also warning of a white pill with the Mitsubishi logo imprinted on it, found to contain the chemicals 5IT or AMT, and a yellow tablet with a star logo.
Officers recovered a large quantity of fake ecstasy tablets at a house in Aberdeen on Tuesday. These tablets are also green but with the Heineken logo.
Superintendent Grahame Clarke, from Police Scotland’s western division, said: “An investigation is under way and our inquiries have so far revealed that the woman, along with three friends, had taken what they thought were ecstasy tablets. The tablets were described as green with a Rolex crown logo stamped on them.
“Public warnings have been issued recently in relation to the dangers of taking ecstasy, or indeed tablets being passed off as ecstasy. They are illegal and could contain a cocktail of toxic ingredients.
“We have yet to establish if this particular pill is to blame for the death of this young woman, but the fact that she and her friends took pills described as green and with a Rolex stamp on it causes us real concern.
“The exact contents of the pills are unknown but they could contain dangerous chemicals and users need to be aware of the dangers and understand the devastating effect they can have.”
Chief Inspector George MacDonald, based in Aberdeen, said following yesterday’s seizure: “The exact contents of these particular pills are unknown at this time. What we have found is that they contain more than one class C drug as well as another dangerous substance, PMA.
“While these tablets do not feature the distinctive Rolex logo found on those in the Glasgow area they do contain the same toxic substance.
“The impact of taking a drug you do not know the exact content of can be extremely dangerous and fatal in some cases.
“Taking it just once can be one time too many and I would urge people to avoid any such pills or drugs and report any information to the police.”
People taking the fake pills can experience symptoms including high temperature, aggression and muscle pains as well as hallucinations and excitability, medics said.
Richard Stevenson, a doctor in emergency medicine at Glasgow Royal Infirmary, said: “These symptoms are treatable if help is sought early.
“I would urge anyone who begins to feel unwell or feels a more intense high than usual after taking any drug which they think is ecstasy or not to seek immediate medical help.”
Police are keen to get the warning across ahead of this weekend’s T in the Park music festival in Balado, Perth and Kinross.
Drugs “amnesty bins” will be available at the entrance to the campsites where illegal substances can be disposed of without risk of prosecution, police said.
Mr MacDonald said: “We want to encourage people to enjoy themselves but our priority is keeping people safe and we want to make them aware of the direct dangers of becoming involved with drugs.”