A Waihi road is likely to remain closed for the rest of the week after a tomo - nearly 2m wide - caved in the surface.
A spokeswoman for Hauraki District Council said the tomo was 4m to 5m deep under the Trig Rd South.
The tomo is one of a series council staff discovered today and the section of road,
near the intersection with Mathers Rd, is now unlikely to reopen this week.
A contractor transporting farm machinery found the tomo last night.
Deputy Mayor Toby Adams, who is also the council's roading and transport portfolio holder, was thankful no one was hurt.
"I'd really like to acknowledge the speed at which both the community and council staff responded to ensure no one was at risk at any point." Investigations were now under way into the cause of the collapse and how to fix it.
Council group manager of engineering services Adrian de Laborde said tomo have been found on both sides of the road, as well as one beneath it.
"Water has run beneath the culvert and formed an underground watercourse that has caused these tomo over time. Recent heavy rain in the area has exacerbated the problem," he said.
Abigger culvert will be installed and realigned over the next few days to prevent a recurrence of the problem.
The road is a popular shortcut between Tauranga and Whiritoa.
The 50m overflow channel in the Wairoa River bar aims to improve flood management.