Results on water samples from Waikato River and water treatment plants are expected today

Auckland's Watercare and Hamilton City Council have reported slightly elevated arsenic levels in recent treated water samples.

There's no immediate risk to public health and the water is safe to drink.

Waikato Regional Council Science Manager, Mike Scarsbrook says they'll know more - once the tests come back.

He says if the samples they took yesterday already show levels going back to near normal, they may conclude it was a spike, and will look to understand why that happened.