A rural Waikato resident has been taken to hospital after discovering a mysterious white powder in their garden.

The person rang emergency services just before 7.30pm to report the powder, bringing a specialist hazardous management fire team and ambulance descending on their home in Poland St in Waikino.

"We sent a Hazmat team around to assess what it was, which they are still determining," a police spokeswoman said.

"But there is no concern for safety."

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The concerned resident came into contact with the powder but were not injured by it.

Instead, a pre-existing health condition kicked in.

"Coincidentally, they were treated for their health conditions, but it wasn't in relation to the powder," the police spokeswoman said.

A St John spokeswoman said one person from the house was taken to Thames Hospital in a moderate condition.

A Fire and Emergency spokesman confirmed they had also attended.