Police in New Zealand are racing to trace down sweets containing “potentially lethal levels of methamphetamine” after they were distributed by a charity in Auckland.

Up to 400 people may have received the sweets from Auckland City Mission as part of a food parcel, said the anti-poverty charity.

The sweets were donated anonymously by a member of a public in a sealed retail package, it added.

At least three people, including a child, sought medical attention afterwards though none are currently in hospital.

“We did not know that the lollies contained methamphetamine when they were distributed,” the charity’s spokesperson told the BBC.

Each individual sweet could have a street value of around NZ$1000 ($601; £468), according to the New Zealand Drug Foundation.

Police say while the incident could be accidental rather than a targeted operation, they had not drawn any conclusions as it is “a bit early to say”.

The charity alerted the authorities on Tuesday after being alerted by a recipient about the “funny tasting” sweets.

Helen Robinson, chief executive of Auckland City Mission, said that some of the charity’s staff members tried the sweets themselves and agreed with the complaints, and started to “feel funny” afterwards.

They then sent sweets that were still on site to the NZ Drug Foundation for tests, which confirmed that potentially lethal levels of methamphetamine were contained in the samples.

In a statement, the foundation said they found about 3g of methamphetamine in a sweet that was sent for testing.

“A common dose to swallow is between 10-25mg, so this contaminated lolly contained up to 300 doses,” says its head Sarah Helm, adding that swallowing such amount of the drug is “extremely dangerous and could result in death”.

Methamphetamine can cause chest pain, racing heart, seizures, hyperthermia, delirium and loss of consciousness, according to the foundation.

According to Ms Robinson, the mission distributes around 50,000 food parcels a year and only commercially manufactured food are included in these parcels.

Police have asked people that have sweets wrapped in brand Rinda’s yellow pineapple flavour packaging to contact them immediately.

“It’s vital the public are aware of these lollies and the hazard that they present,” Detective Inspector Glenn Baldwin said in a press conference on Wednesday.

Describing it as a “deeply concerning” matter, he said that such cases of food laced with meth had happened before and they would likely work with Interpol on the investigation, which may take some time.

Rinda, a Malaysian confectioner, told BBC News that it has come to their attention that their products may have been misused in connection with illegal substances and the company “does not use or condone the use of any illegal drugs” in their products.

“We will work closely with law enforcement and relevant authorities to address this issue and protect the integrity of our brand,” the firm said in a statement.

Steven Peh, the general manager of Rinda, told local news site Stuff NZ that the contaminated candy he had seen in photos was white, whereas Rinda’s product is yellow.

The authorities are still trying to understand the scale of the spread. 16 packets have been recovered so far – police say each packet could possibly contain 20 – 30 sweets but they don’t know the exact number in the 16 packets. Up to 400 people have been contacted by the charity.

Ms Robinson said the sweets likely came into the charity’s posession in about mid-July, but that they are calling everyone as far back as 1 July to be safe.

Ben Birks Ang, deputy director of the NZ Drug Foundation, said the organisation believes the incident was unlikely to be intentional as “disclosing substances as something else to smuggle it into another area is common”.

But there are still fears that other charities could be affected.

Ms Robinson said she had contacted other charities to check for their sweets.

“To say we are devastated is an absolute understatement,” she told the press, adding that one in five in New Zealand experience food insecurity, which makes the incident “deeply distressing”.