People who travel between Tauranga and Rotorua via State Highway 36 are being warned to prepare for an urgent overnight road closure.

Crews working in the Mangorewa Gorge have found a collapsed stormwater culvert under the highway near the recent underslip work.

A NZ Transport Agency Waka Kotahi spokesperson says as the culvert runs under the full width of the road it urgently needs to be replaced.

"NZTA advises, for both the public and site crew safety, the road will be closed overnight next Monday so it can be replaced.

"While we have the opportunity, and to provide greater resilience, the culvert will be upgraded with a new 450 diameter pipe"

The overnight closure is planned for Monday, Septermber 16, from 8pm to 4am.

During the full closure the detour for all vehicles travelling between Pyes Pā Road and Hamurana will be via SH29A, SH2 Tauranga Eastern Link Toll Road (or Te Puke Highway), continuing to SH33 through Paengaroa, then SH30 and SH30A through Rotorua, turning right onto SH5 and rejoining SH36 at Ngongotahā.

"NTZA appreciates road users’ understanding while this vital work to repair the highway is being completed."