One lane of the main highway north of Wellsford is now open after a truck and trailer crash early this morning.

A crane is being brought in to right the large truck after it rolled on SH1 at Brynderwyn about 4am.

Motorists are being warned to expect queues and delays while traffic is ushered past the crash site by stop/go signs on the northbound passing lane.

Police said a truck and trailer unit rolled between Baldrock Rd and SH12. The driver suffered moderate injuries.

The highway was closed to allow a crane to be brought in to right the truck and trailer.

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It is not yet known when it will be fully reopened.

Diversions are in place along Mountain Rd and SH12.

The truck driver suffered moderate injuries in the crash.

A Fire Service spokesman said a truck rolled near the Northland town of Kaiwaka about 4am.

The New Zealand Transport Agency warned motorists to expect delays.

"Emergency services are on site. Please delay your journey or use an alternative route," NZTA said on its website.

Northbound drivers can take Kaiwaka-Mangawhai Rd, onto Moir St, left onto Molesworth Dr, left onto Mangawhai Heads Rd, right onto Cove Rd, before continuing through Waipu and back to State Highway 1.