In the latest incident in Scotland, an 18-year-old woman died in West Dunbartonshire on Tuesday morning. Three male friends were also admitted to hospital for treatment.
The green pills with a crown logo, thought to be five times as strong as ecstasy, are being blamed.
"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," Superintendent Grahame Clarke, from Police Scotland, said.
In Northern Ireland, it had been feared that eight unexplained deaths of people in their 20s and 30s in the space of four weeks had been caused by the same drugs.
However, it was later established that no single killer drug was responsible.
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.
Authorities continue to warn about the dangers of the 'rolex' pills though, after they were found to contain a dangerous stimulant known as PMA.
Other drugs believed to have been mistaken for ecstasy have also been seized in Scotland.
They include white pills with Mitsubishi logos, yellow tablets with star logos and other green pills with Heineken logos.
The exact ingredients are not yet known, but all the pills are feared to contain a toxic mix of a number of chemicals, including more than one Class C drug and PMA.
According to medics, those taking the drugs can experience symptoms including soaring temperatures, muscle pains, hallucinations and aggression.
Police in Scotland are particularly keen to get the message about the dangers out to people ahead of this weekend's T in the Park music festival in Balado, Perth and Kinross.
Meanwhile, officers in Northern Ireland have been accused of not doing enough to combat drugs, with community leaders claiming even "the dogs on the street" know who the dealers are.
"We don't speak dog," Detective Chief Superintendent Roy McComb hit back.
"If people know, we would rather they picked up the phone and spoke to our Organised Crime branch."