One person remains in hospital after Friday night's Listen In festival in Auckland.
Three people were rushed to hospital in a critical condition after taking unknown substances at the event held at Mount Smart Stadium where a 20,000-strong crowd had gathered.
The injuries occurred at EDM concert Listen In 2019 with all the three people, plus two others who sustained more minor injuries, taken to Auckland Hospital, a St John spokesperson told 1 NEWS yesterday.
St John head of public affairs, Victoria Hawkins, confirmed to 1 NEWS the incidents involving the three critical patients were substance-related, but added they "can only treat anything ingested as a poison".
"Obviously they ingested something. As to what that is, we’re not sure," Ms Hawkins said.
It comes amid debate over whether the testing of drugs at music festivals should be made legal.