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Senior Sergeant Paul Robertson told the Herald that Police didn't want to see a repeat of last year's festival, which saw a number of people hospitalised for drug-related issues.
He also said that police were concerned about the presence of high-dose MDMA (ecstasy), and dangerous cathinones (like N-ethylpentylone and eutylone) in the New Zealand music festival scene this year.
Similar drugs have led to deaths overseas and had seen dozens hospitalised in NZ, he said.
"These substances are being distributed for profit with little regard for the wellbeing of the person consuming them.
"These substances may be offered to you in the lead-up to, or during, the Electric Avenue music festival.
"Our advice is that it is safest not to take any substance that you do not know the origins of."
Police advised festival-goers to visit the Know Your Stuff NZ website for further advice and look after their friends and seek medical help in the event they are adversely affected by drugs.
They also reminded those attending to watch their alcohol intake and drink responsibly.
The warning echoes previous alerts this summer about high-strength MDMA.
On December 30, drug-related harm-reduction service Know Your Stuff issued a warning about dangerously high-dosage MDMA pills circulating the country.
"These pills should be approached with caution," said Know Your Stuff, which operates independently throughout New Zealand with the support of the New Zealand Drug Foundation.
"Users are advised that the only way to guarantee safety is to not take them. For those who do choose to take them, our recommendation is to only take a third of a pill at most, and wait at least an hour before considering taking any more."
Pills tested were found to contain MDMA and a variety of fillers, with one type of pill (Pink Mitsubishis) containing caffeine, which can increase the risk of heart problems and psychosis. No other psychoactives were detected in the listed pills. Others by names of Yellow Ironman, Blue Punisher, White CNN and Blue New Yorker, and Yellow New Yorker were all found to have around three times the common dose of MDMA – which is around 80-120 milligrams.
In 2018, a batch of drugs being passed off as MDMA was actually n-ethylpentylone - three times stronger than ecstasy – and resulted in 13 people being admitted to Christchurch Hospital, including a 15-year-old.
The Electric Avenue festival, held in North Hagley Park, is the biggest outdoor summer festival in Christchurch and attracts thousands to listen to international and local acts.