Hundreds of sweets were donated to a charity and sent to families – now authorities are pleading that no one eats them after a deadly discovery in the wrappers.

New Zealand authorities are urging Kiwis not to eat a specific brand of candy after drug tests revealed a potentially lethal amount of methamphetamine.

The New Zealand Drug Enforcement Foundation carried out a drug test on a white candy found in a Rinda brand pineapple packaging and found it contained three grams of the illicit drug.

The test was carried out after a mother unwittingly gave her son a candy laced with methamphetamine before he immediately spat it out.

“A common swallowable dose is between 10 and 25 mg, so this contaminated candy contained up to 300 doses,” said NZDF chief executive Sarah Helm.

“Swallowing so much methamphetamine is extremely dangerous and could cause death.”

The treats were distributed by the Auckland City Mission after being donated as part of food parcels.

Auckland City Mission chief executive Helen Robinson said she was devastated.

It is believed that between 300 and 400 people may have received the packages and efforts are being made “urgently” to contact them.

“The mission only accepts commercially manufactured foods… and the candy appeared as such when it was donated,” he said.

“It was very appropriate for our staff to believe that this was a safe candy. It came in a sealed, unopened package, and the candies were individually wrapped.”

Ms Robinson said she knew of eight families affected. No one had been reported sick or injured.

The NZDF said the discovery of the sweets vindicated its legalised drug control system and communications networks.

Deputy Chief Ben Birks-Ang said there could be more candy lying around, suggesting they could be part of a botched drug deal.

“We know that disguising substances as other things in order to smuggle them is common internationally,” he said.