Almost a dozen people are in hospital in Newcastle after allegedly taking drugs in the form of a blue pill emblazoned with the Superman logo.
Ten men and one woman were hospitalised in the Newcastle suburb of Waratah between Friday night and Monday night.
They are all believed to have ingested the same blue tablet.
Newcastle City Duty Officer Inspector Shane Buggy issued a warning in the lead-up to Newcastle's festival season.
"This could have been a tragedy - thank goodness it wasn't," he said in a statement on Wednesday.
"We can only hope those involved are fine but also learn a lesson."
"There is no such thing as a bad batch. These pills are made by criminals in backyard labs and might be sold as one substance but are actually another."
Investigations are continuing into the matter.
