A charity for homeless people in New Zealand issued an apology on Wednesday for handing out candy that contained lethal amounts of methamphetamine.

The Auckland City Mission, which donates parcels of essentials to New Zealanders who cannot afford food, said it first became aware of the issue on Tuesday afternoon when some recipients complained about the foul-tasting candies.

Three people - a child, a teenager and a charity worker - sought medical treatment after tasting the boiled sweets, though none are currently in hospital, Detective Inspector Glenn Baldwin from Auckland police told reporters.

There was no suggestion of wrongdoing by the charity, he added.

"To say we are devastated is an understatement," the Mission said in a statement.

The candy, which was donated by an unknown member of the public, was tested by the New Zealand Drug Foundation charity, which found they contained a potentially lethal 3 grams (0.1 oz)of methamphetamine.

"A common dose to swallow is between 10-25mg, so this contaminated lolly contained up to 300 doses," said foundation Executive Director Sarah Helm.

Police believed the candies were the byproduct of an international drug trafficking operation and have called for them to be handed them over to the authorities. They are also investigating how the candies entered the country, Baldwin said.