A massive rockfall has been caught on video as it cascaded down the side of a Coromandel cliff onto State Highway 25.

The rockfall at Rumahanga Bay closed the road between Tapu and Waiomu on Wednesday evening.

The slip was approximately 500m north of the Ruamahanga boat ramp.

A video shows rocks, trees and debris falling from a cliff face and smashing onto the road with cars lined up on the road just metres away.

Watch the video below.

Part way through the rockfall, the first car in line, a silver vehicle starts reversing from the slip as rocks are still falling.

Other people can be seen out of their vehicles watching the slip happen, including people in high-vis and hard hats.

Waka Kotahi says it wouldn't be cleared overnight.

Rumahanga Bay is around 16km from Thames.

The transport agency advises against non-essential travel in the Coromandel and parts of east Waikato due to the road conditions making travel hazardous.

State Highway 25 has been compromised in many areas with multiple slips, surface water, mud and other debris on the road.

People can expect delays as contractors work to clear it.

Meanwhile, State Highway 25A remains closed after the road collapsed.

State Highway 2 through the Karangahake Gorge is open following the clearance of two slips. It was down to one lane overnight as the embankment is still saturated and active.

In west Waikato, the road between Raglan and Hamilton was closed overnight due to the severity of cracking and slumping of SH23.

State Highway 23 between Hamilton and Raglan was closed on Wednesday night and is to be re-assessed on Thursday morning. Photo: Waka Kotahi.

Waka Kotahi NZ closed it to all traffic overnight from 7pm on Wednesday.

'We have been doing everything we can to keep this road open but a geotechnical inspection late this afternoon has confirmed the risk to the travelling public has increased,” says Waka Kotahi system manager for the Waikato, Cara Lauder.

'Despite our best efforts to keep water out of the cracks, the fissures are growing.”

For public safety the road was closed and is to be re-assessed on Thursday morning.

'As well as applying cold mix asphalt to the cracks, an asphalt bund was added to direct road water flow away in an effort to prevent further damage, however it hasn't been enough to stop it getting worse.”

A detour is in place via Ohautira Rd, Waingaro Rd, Herschel St, Ellery St, Whatawhata Ave, Ngāruawāhia Rd, Horotiu Rd to re-join SH23.

Caution is advised on the detours as they are tight, winding roads.

- Jo Lines-MacKenzie/Stuff.