Six children who took what police believe were so-called “legal highs” ended up in hospital.
Police have issued a warning over the potentially deadly psychoactive substances following the incident in Cleveleys on Tuesday.
People should not take them as they simply have no idea what they could contain or the health risks involved.
In a statement, Lancashire Police said it was “unhelpful” that the fact they can be sold legally means people often assume they must be safe.
The boys, all aged between 10 and 15, were all taken ill in the car park of The Venue, on North Promenade, after taking an unknown substance.
The youngsters were taken to Blackpool Victoria Hospital and have since been discharged. Detectives are now investigating to establish what the substance was.
A Lancashire Police spokesman said: “We’re warning people to be careful after six boys were admitted into hospital after taking an unknown substance.
“We were called by the ambulance service at around 12.50pm following reports that the boys, who are all from the Thornton and Cleveleys areas and aged between 10 and 15, had been taken ill in the car park of The Venue after taking what is thought to be some sort of ‘legal high’.
“They have all now been discharged from Blackpool Victoria Hospital and enquiries are on-going to establish exactly what the substance is.
“Thankfully the boys are now recovering but the outcome could have been very different.
“Our advice on new psychoactive substances, or what are sometimes unhelpfully referred to as ‘legal highs’, remains that people should not take them as they simply have no idea what they could contain or the health risks involved.”
Police said it had reported the incident to Lancashire County Council’s health department.
For information about so-called legal highs, visit www.talktofrank.co.uk
Have you been affected by legal highs? Call our newsdesk on (01253) 361733.