The mother of one of the six Hamilton girls hospitalised after taking tainted pills at school has been charged with drug possession.

Her daughter has been referred to Youth Aid for supplying the pills to her friends.

Six Fairfield College pupils, as young as 13, swallowed the small pink pills with a bird stamped on them in the belief they were ecstasy.

They reacted aggressively when admitted to Waikato Hospital's emergency department.

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Police said analysis by scientists found the pills were made up of BZP - the active ingredient in recently banned party pills - and other controlled substances.

Earlier reports said the pills were the class B drug ecstasy.

Hamilton City Area Commander Inspector Rob Lindsay said a 38-year-old woman has been charged with possession of a class C controlled drug.

Her daughter had been referred to Youth Aid for allegedly taking the pills to school and supplying them to other girls.

The investigation was ongoing and it is likely there will be more referrals to Youth Aid, Mr Lindsay said.

"What this incident has shown us is that a percentage of young people are vulnerable from making wrong decisions and there are consequences from those decisions."

Referring the girls involved in the case to Youth Aid would not be solely to punish them, Mr Lindsay said.

"An objective of the referrals is to ensure the appropriate support services are made available to the young people concerned and that this support is ongoing, to do this we will be working with the teenagers and their families to achieve this."

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Auckland police earlier said they were investigating whether the pills the girls took are linked to an alleged criminal syndicate in Auckland which made tens of thousands of designer drug tablets each week.

Detective Inspector Bruce Good, head of the Auckland metro drug squad, confirmed he had contacted police colleagues in the Waikato after the scare.

Once ESR tests on the Fairfield college pills were complete, Mr Good said the results would be compared with the tablets seized in the 12-month Operation Ark which led to 21 arrests and $14 million of assets being frozen last week.

"My team are going through the mountain of stuff we have. Once ESR has completed the report [in Hamilton], we'll ... see if any links exist."

When announcing the Operation Ark arrests 10 days ago, Mr Good said the alleged syndicate was responsible for 80 to 90 per cent of the Ecstasy market in New Zealand.