Police have issued a warning to recreational drug users that what they think they are buying is probably not what they are getting.
A worldwide decrease in the availability of ecstasy means other synthetic drugs are taking its place, and they are coming in all sorts of varieties and with all sorts of effects.
That is leading to hospital admissions, and hundreds of hours of police time spent trying to identify new chemicals used in the drugs.
They look like any other pills - designer drugs said to have the same effects as ecstasy, but according to police they are cheap knockoffs and could be even more harmful.
“The big danger is that you don't know exactly what's in them. There's all sorts of different things that can go in them, all sorts of changes can be made to their chemical balance,” says detective senior sergeant Chris Cahill, of the Auckland Metro Drugs Squad.
The drugs have become more common on the streets of New Zealand than ecstasy.
And police are spending increasing amounts of time trying to trace them and find out exactly what is in them.
They believe the increase follows the banning of party pills and a world wide decrease in the availability of ecstasy.
Police say many are buying the designer drugs believing they are ecstasy.
That confusion has led to hospital admissions after people have accidentally overdosed.
“They expect the instant buzz you might get out of, whether it's methamphetamine they may have tried or cannabis but these pills, I mean you might have taken four or five trying to get the reaction and then suddenly they all come on at once,” says Mr Cahill.
Late last year Auckland police seized 6000 4-mec tablets - a drug with similar effects to cocaine.
But police are finding new variations all the time.
“And that's the concern that you could be taking one thing one week, and have one sort of reaction, the next week you have it and it could be a totally different drug even though it's called the same thing, you could have a much more adverse reaction,” says Mr Cahill.
The drugs are usually smuggled into the country in tablet form and sell for about $20 to $40 a pop.
Police say they will have a presence at tomorrow's Big Day Out in Auckland - their focus will be on trying to catch the dealers rather than the users.
“We'd be naive to say there's not a fair few pills popped at the Big Day Out. Our concern is two fold, you don’t know what you're taking now days, there's a lot more out there and you're in a totally different environment. There are a lot more people around and you may feel uncomfortable and have different reactions,” says Mr Cahill.
Some of the designer drugs are technically legal, because authorities have not had time to classify them as illegal. But police warn the classification process does not take long, and charges can be laid retrospectively.