A super-strong batch of ecstacy pills has made several children in Yorkshire ill and prompted the council to issue warnings to schools attended by thousands of pupils.
The orange "Tesla"-stamped tablets are reported to each contain 240mg of MDMA – around double the current UK average, which has risen dramatically in recent years.
North Yorkshire County Council declined to give details of the number of children hospitalised, although it is understood that none are in a critical condition.
"I understand there were problems at one school so we decided to distribute the letter as a wake-up call," Council leader Carl Les told The Northern Echo.
"We should always be very vigilant and it is right to advise parents on these sorts of issues when they arise. From my experience these are very rare circumstances, but they have such a high impact. We are right to be cautious."
Drugs harm-reduction experts, The Loop, tested the orange Teslas in September 2016, alerting users to the high concentration of MDMA.
The quality of ecstacy pills plummeted in the UK during the noughties after Cambodian and Australian law enforcement seized enormous quantities of safrole – a naturally occurring oil needed to produce MDMA. The DrugWise think-tank estimated that half of all ecstasy pills seized in 2009 contained no MDMA.
Then in 2010, Chinese chemists developed non-safrole precursor, PMK glycidate, which enabled ecstacy manufacturers in Europe and beyond to greatly improve their product.
DrugWise estimates that UK ecstacy pills are roughly twice as strong today than they were in the highly mythologised early 1990s.
The Orange Teslas seized in North Yorkshire are twice as strong again, meaning that consuming an entire pill could cause serious damage to a young person.
In a statement sent to pupils and parents at six schools, Dr Lincoln Sargeant, the council's director of public health, said: "Unfortunately, there have been some cases of use by young people in the local area that has resulted in them being hospitalised.
"Parents/carers are asked to be alert to this issue, particularly any mention of Orange Tesla tablets as these are being used in the area currently."
There were 63 ecstasy and MDMA-related deaths in the UK in 2016 – the highest number on record.