State Highway 25, between Hikuai and Opoutere, remains closed this morning following further collapse of the underslip overnight.

Convoys were allowed through for a short window this morning, but Waka Kotahi NZ Transport Agency advises the highway needed to re-close once the convoys were cleared.

The closure is to allow allow urgent work to continue, says a spokesperson for the roading agency.

"Contractors are cutting further into the hillside to widen the road further away from the underslip.

"The road was originally closed early Monday morning following a washout caused by heavy rain over the weekend.

"Expect another update early afternoon or as soon as the situation changes."

SH25A and SH25 are currently closed.

Meanwhile, SH25A between Kopu and Hikuai remains closed.

Part of the highway collapsed following a large washout on January 27.

It is not yet know when the road will be re-opened.