The assessment and clearance of slips on State Highway 1 through the Mangamuka Gorge stopped at the summit last week because of continuing movement after three days of torrential rain.

The deluge left eight significant slips and many smaller ones along a 12 km stretch of SH1 through the Gorge, while another slip appeared to be forming south of the summit and the three biggest slips on the northern side were still moving, Waka Kotahi NZ Transport Agency Northland system manager Jacqui Hori-Hoult said.

Road clearing crews have moved their equipment away from the summit.

"There's a huge safety issue for our workers at the moment, and we'll just have to wait rather than compromise on that," Hori-Hoult said.

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"We'll also be putting up a drone so we get a view of what we can't see from the road. There may be other slips and instability above the road in places, and we need to take that into account.

"The major overslip closing the road starts well up the hillside, and there are big trees left hanging where the ground has fallen away. With expected rain and high winds this could loosen up more material to fall on to the road."

It wasn't just the slips above the road that were still moving either. Half the width of the road had slumped in one place, photos showing that it had dropped further over the previous couple of days.

The slips were smaller on the southern side of the gorge, and road crews had been working to clear them.

"It may be possible to open the gorge to light vehicles, with the road in places reduced to one lane. We'll know more on that (this) week. The team is working hard to ensure it is safe to open the road," she added.

For now, SH1 was closed between Victoria Valley Rd in the north and Makene Rd in the south, with SH10 as the detour, adding 20-30 minutes to the journey from Kaitaia to Pakaraka.