The Transport Agency is working with Civil Defence, emergency services and local authorities to support people in the area who may be affected.
Facebook user Troy Denison posted a photo of the dramatic damage with people standing by the crevasse in the road, staring in disbelief.
State highway 1 closed south of pukenui
Posted by Troy Denison on Thursday, 22 March 2018
Local tow truck driver Crunch Bradley said the washout happened on land he previously owned, on State Highway One about 200m north of Ariawa Rd.
His daughter now owns the land on one side of the washout, and his son the land on the other.
He said heavy rain caused part of a newly built footpath to slump and block a culvert, which caused the water to back up, before it let go and washed the road away.
"Now there's a 35 foot [10.5m] hole."
He said while there was no official way around it, people could go via forestry roads in the Aupouri Forest, or down Ninety Mile Beach.
Drivers could turn off State Highway One on to Trigg Rd when heading south, or Hukatere Rd when heading north to go via the forest.
Mr Bradley said cars could use the forestry route but it was rough and had some loose metal and was not was well signposted.
The Four Square in Pukenui was busy with people stopping for supplies and some staff members were unable to get home.
Pukenui Holiday Park owner Jo Kennedy said the washout was about 3km south of Pukenui.
She had not had any extra people turn up to the park to stay as she said people had been using the forestry roads to get around.
Fishing competition Snapper Bonanza, which runs until Saturday on Ninety Mile Beach, posted a photo of the washout on their Facebook page, and told competitors to drive down the beach.
Ahipara Backpackers and Motor Camp owner Sandy Ratcliffe said none of his guests seemed stressed about the situation but was surprised the road had caved in.
"It's unbelievable," he said. "I didn't think it was that much rain. It was certainly heavy but nothing that we haven't been experiencing every winter.
"I'm sure there will be a lot of pressure on [officials] to get it repaired. We're in peak season."
Hukatere Lodge founder Gabrielle Pfaender said the Far North always got the "bad end of the stick" weather-wise and hoped the road would be fixed quickly.
She said it had been pouring with rain all night but the sky was starting to clear.
