Cyclone Gabrielle: More than 4500 people have been reported as uncontactable

More than 4500 people have been reported as uncontactable after Cyclone Gabrielle, with 900 people found, according to Police Commissioner Andrew Coster.

Coster has spoken to media this afternoon at the Hawke's Bay Emergency Management Group Centre in Hastings.

He said the scale of devastation was significant and he was blown away by the work police were doing as they had also been badly affected.

But he said there was no indication that the number of deaths was significantly larger than the seven that have been confirmed so far.

He said there was still a lot of work to do searching homes and if people were found, their family would be contacted first and media told.

Meanwhile, people in Gisborne are being warned to stop using water immediately until further notice.

The Gisborne District Council says the water treatment system has failed.

Council manager Scotty Sharp says people need to "stop all use right now".

"Everything, absolutely everything," he says.

"Critical, it's absolutely critical. We need to get the info out to the public because it's just failed and it's just failed now."

Sharp says the council doesn't know why it's failed, but silt could have overloaded the system.