Up to eight people are believed to be injured following a serious crash involving a truck and three cars on State Highway 1 at Hunterville.
Initial indications suggested up to three people could be seriously injured, and a number of others have received moderate or minor injuries.
The State Highway was closed for several hours and re-opened late tonight. Police thank motorists for their patience.
The Serious Crash Unit has examined the scene and enquiries into the circumstances of the crash are ongoing.
Police are also attending a crash on the Hawkes Bay Expressway where one person is believed to have received moderate injuries. Diversions are in place.
The crashes come as people returning home from school holidays are urged to drive carefully after a series of road closures around the North Island.
Parts of the Mangamuka Gorge in Northland and State Highway 25 and 25a on the Coromandel Peninsula remain closed this afternoon after heavy rain caused slips and flooding.
Waka Kotahi NZ Transport Agency is now asking motorists to be patient as contractors worked hard to try and clear the roads.
However, Waikato system manager Cara Lauder this afternoon confirmed SH25 and SH25a would remain closed today due to slips blocking the roads.
SH25A between Kopu to Hikuai is closed overnight, with further geotechnical assessment ongoing, while SH25 between Hikuai and McBeth Rd in Opoutere will also remain closed, she said.
With children back to school tomorrow and Coromandel holidaymakers heading home today she asked people to consider delaying their travel where possible.
"The detours for these closures will add considerable time to your journey, with motorists who would normally use SH25A directed to use SH25 via Coromandel and Whitianga and those travelling south of McBeth Rd in Opoutere on SH25 directed to use State Highway 2 through the Karangahake Gorge."
She urged motorists to expect more traffic on the roads, keep an eye out for unreported hazards and reduce speed.
"We want to see everyone arrive home safe."
Meanwhile, in storm-battered Northland, many roads were reopening with the severity of the heavy rain today being revealed.
At least seven large and several small slips are littered through the gorge, with some even breaking the tarseal.
NZTA area system manager Jacqui Hori-Hoult said further rain forecast for the region could lead to more surface flooding in low-lying areas and slips.
NZTA media manager Darryl Walker said roading staff were still assessing how to combat the clean-up given there was rain forecast over the next couple of days.
"Conditions could change. It's been pretty wet. Rivers are still quite high so there's a possibility we might need to close roads again, but at this stage they're all open."
The agency said it was likely the road would be closed for several days and a detour in place via State Highway 10 would add 20-30 minutes to most journeys.
On the East Coast, SH35 was closed between Ruatoria and Tolaga Bay.
Severe weather had caused multiple slips and potholes along with flooding.
NZTA is due to post an update as to whether it would re-open this afternoon, however occasional rain is due in the area for the next 48 hours, according to the MetService.