More than 15 festivalgoers were hospitalized for overdoses at the Electric Parade dance music festival in Melbourne, Australia on Saturday night. It is reportedly the highest number of overdoses seen at a music festival in recent times.

The drug that contributed the most to these overdoses was GHB or synthetic GHB. GHB is a sedative used both as a prescription sleep-aid and as a recreational intoxicant, according to erowid.org. It is known for its ability to induce a short (several hour) coma-like sleep at high doses.

Paramedics treated 46 Electric Parade attendees for various conditions, with 22 taken to the hospital.

Victoria state health commander Paul Holman said “We’ve transported 22 people from that event alone, and we’re now up to 30-plus from that event and across the city, all with GHB overdoses, all critically ill.”

In addition to overdoses, another 40 were arrested during the festival, 28 people received diversions and two received cannabis cautions. One man was charged with possession of ecstasy, cocaine, MDMA, LSD, ketamine and hashish.

This incident continues to open the discussion about music festivals supplying drug-testing kits.

Event organizers have been contacted for comment.