MDMA linked to Listen In hospitalisations, four arrested for climbing marquee

Concertgoers hospitalised on Friday night are suspected to have consumed the illicit substance MDMA, police have revealed.

Three people were rushed to hospital in a critical condition, with a fourth in a serious condition, on Friday night after becoming ill at the Listen In festival at Mt Smart Stadium.

St John paramedics understood the four individuals had consumed something, but were initially not sure what substance it may have been.

But it's now believed it was MDMA - often referred to as ecstasy.

"Police were made aware that several people attending the event required hospital treatment after consuming what the users believed to be the illicit substance MDMA," a statement from Auckland city operations planning manager Inspector Siaosi Fanamanu said on Sunday night.

"We have spoken to some of these people who have admitted they did not know what was in the substance they were taking."

Fanamanu said police have provided "prevention advice" to the people about the use of illicit drugs, noting there are "inherent risks" for any users as there is no way of knowing what they are taking. 

"Our advice to those using these drugs is simple - the easiest way to prevent yourself from the harm associated with them is to not take them in the first place."

Police have also revealed that four people were arrested for disorderly behaviour relating to the climbing of the large marquee at the event. 

The festival boasted Australasia's largest marquee, which was erected on the pitch at Mt Smart on Thursday. Video sent to Newshub shows concertgoers climbing the marquee and playing on it as other attendees watch on.

Three people can be seen gallivanting on the roof in the video while the party continues underneath. The marquee reaches about 25 metres in height. Other video sent to Newshub shows attendees climbing the support beams for the marquee while the music plays.

Fanamanu said despite the arrests and hospitalisations, police were "pleased with the behaviour of those attending". 

"In the coming weeks, and as is our standard practice with events of this nature, we will undertake a debrief with the organisers of the Listen In festival and other involved parties.

"This will assist in the identification of areas of concern or any risk behaviours and enable measures to be put in place so organisers can improve the experience for concert-goers at future events."