Strathclyde Police issued a warning to the public and drug users about the dangers of a potentially deadly substance that is circulating in the Lanarkshire area.
The red or yellow coloured tablets are being sold as ecstasy.
They are known as "Rockstar", and normally have a star logo on them.
The exact contents of the pills are unknown but they could, from past experience, contain a cocktail of different substances.
Over the weekend, seven people were hospitalised in the Lanarkshire area after suffering adverse reactions to the pills.
All seven have since left hospital.
Chief Inspector Fraser Lamb, of Strathclyde Police, said: "These substances are unreliable, unpredictable and potentially very dangerous.
"Users may believe that they have taken ecstasy, and it is very likely that they will suffer a negative reaction.
"Symptoms reported include increased heart rate, elevated core temperature and seizures.
"Extensive police enquiries are ongoing to establish the source of these drugs."
Detective Sergeant Michael Miller added: "I would strongly advise people to avoid such pills and report any information to the police or by contacting Crimestoppers anonymously on 0800 555111."