At least five people have been hurt in a two-car crash in Northland that temporarily closed State Highway 1 in the area.

Two people are in a serious condition and have been taken to hospital, while three others escaped with moderate injuries, a Hato Hone St John spokesperson said.

The stretch of SH1 near Puhipuhi Rd, north of Whakapara, has re-opened after being closed after the 2pm crash.

Earlier, a “large rockfall” obstructed Auckland’s SH1 for four hours, delaying and diverting traffic.

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The rockfall, which has since been cleared, happened between Wayby Valley Rd and Wilson Rd in Dome Valley at about 7.55am on Tuesday.

At midday, Waka Kotahi New Zealand Transport Agency announced the road was “fully open again”.

The blockage forced many travellers to backtrack and take an alternative route through SH16.

Truck driver Patrick Klijn was passing through Dome Valley at about 7.20 on Tuesday morning when he saw large rocks near the cliff side.

“I was warned by another truckie when I came around the corner,” he said. “He moved a large rock out of the way for me, so I could pass.”

Klijn drives through Dome Valley three or four times a week but had never seen a rockfall like this scattered over the tarmac.

“There were trees hanging over the barrier. There were quite a few rocks on the northbound lane – all across the road,” he said.