A 15-year-old was amongst the 13 people admitted to a Christchurch hospital over the weekend after taking faulty ecstasy.
Nine festival-goers from Saturday's Electric Avenue were hospitalised later that night, with a further four people reporting to hospital Sunday.
They were suffering from elevated heart rates and dangerously high blood pressure.
A group that covertly tests drugs at music festivals isn't surprised by the result.
Wendy Allison, a director at Know Your Stuff, told Heather du Plessis-Allan during their recent testing they've found extremely high doses of MDMA in pressed pills.
"So it is actually what they think it is, but there is actually a hell of a lot more of it. We're talking two to three doses, we've found a lot of those here."
Allison would like to see the misuse of Drugs Act updated to allow legal testing to prevent further harm.
It's understood all but one of those affected by the bad drugs have since been discharged.
LISTEN TO WENDY ALLISON TALK WITH HEATHER DU PLESSIS-ALLAN