People are being asked to avoid Lake Road in Rotorua after a fumerole has open up on the road.

Rotorua Lakes Council says a fumarole (steam driven event) has appeared in a traffic island on Lake Road this morning, which also created a crack in the road.

"We are currently determining the cause, but it is likely to be linked to high ground water levels (weather driven)," says council says in a post on its Facebook page.

"Please avoid driving through Lake Road right now if you can and find alternate routes.

"Traffic management is in place and one lane is closed on Lake Road while the area is being assessed. We will keep you posted."

RLC geothermal inspector Peter Brownbridge, who was at the scene, says he's not entirely sure why the fumarole popped up where it did.

'We are turning off some of the local geothermal bores, just to be safe,” he says.

'This is not a known hotspot, so it is unusual.

'If it's not the local wells we will have to let it do its thing and just wait. But, it could be moving underneath the road surface.”

He says there are no records of any hot springs where the fumarole appeared.

'The fumarole is not particularly large, it popped up amongst plantings in the middle of a traffic island, but there's a fair bit of water and mud on the road on the side going into town, so we've closed that off for now.”

It is not known if the crack across both lanes on the other side of the road is related to the fumarole.

'We're not detecting any heat or movement from the crack so that side of the road remains open for now.

'Some geothermal bores in the area have been shut down to see if it has an effect on what's happening here, in which case it could be bore-related.

'We have well drillers here now looking to quench one of the bores to see if that affects the flow of water coming out of the fumarole.”

-Additional reporting by Stuff/Matthew Martin.