The Northland Regional Council says mercury found in streams at Puhipuhi near Whangarei is no threat to human health.
An anti-mining group said tests done by the council and local hapu showed high levels of mercury, and it was worried an abandoned mercury mine was polluting the local waterways.
The council said the area is naturally rich in mercury.
Its Maori advisory council chair Dover Samuels said the mercury levels in the streams still met the drinking water standard, although they were higher than in other areas.
He supported the group's call for monitoring, and the remediation of the old mine workings and quarry nearby.
"I would support any application for a rehabilitation fund and a plan to rehabilitate that whole area back to its original landscape as much as possible."