The New Zealand Drug Foundation have arranged drug testing clinics in Wellington and Masterton this week after a powerful synthetic opioid was discovered over the weekend.

An investigation into the source of powdered fentanyl is under way after 12 people were hospitalised in Wairarapa over 48 hours following the drug being sold as methamphetamine or cocaine.

This is the first time powdered fentanyl has been found in New Zealand.

The Wellington clinic will run from 5pm to 7pm Wednesday at 233a Willis Street and the
Masterton clinic from 12pm to 4pm at Drugs Project Masterton, 17a Hope Street.

"This is in response to preliminary testing detecting fentanyl in white powder sold as cocaine and meth that's led to 12 hospitalisations in Wairarapa," the organisation said on Twitter.

In the post, the Foundation wrote that drug testing was free and legal, and they do not take any personal information.

"You only need to bring in a small amount of the substance you want checked (about a matchstick head's worth)," the post said

Detective inspector Blair MacDonald, Manager National Drug Intelligence Bureau, said one gram of pure powdered fentanyl is the equivalent of 20,000 safe doses of the drug.

Those hospitalised displayed the same symptoms as an opioid overdose and at least six of them were unconscious and in serious condition when emergency services arrived.

The white powder has a very similar appearance to cocaine and authorities are warning it should not be consumed in any amount.

"The discovery of powdered fentanyl in New Zealand is of significant concern, due to the harm caused internationally by the synthetic opioid," MacDonald said.

"Just one gram of pure powdered fentanyl is the equivalent of 20,000 safe doses of the drug."

He said in North America last year, more than 60,000 people lost their lives due to a fentanyl overdose.

"We do not want to see that type of harm occurring in our communities," MacDonald said.

"Police are now working urgently to determine the source of the drug, and its prevalence in the community."

• Anonymous reports of the drug can be made through High Alert's reporting system for unusual effects using the alert ID N22/029.