Two commercial vehicles travelling in opposite directions on State Highway 2, both with a punctured and leaking diesel tank, likely caused multiple crashes and spin-outs across a 50km stretch of Hawke's Bay highway.
Emergency services were alerted to the first spill, by a driver travelling north through Hawke's Bay from Dannevirke, at 8.15am today.
Fire and Emergency NZ Hawke's Bay area commander Ken Cooper said the man "suddenly realised he was running out of diesel, pulled over and realised that he had a punctured diesel tank".
The two vehicles were unrelated. The other vehicle was travelling south, Cooper said.
Firefighters said the spillage from both vehicles covered a "fair bit" of State Highway 2 from Waipukurau to Hastings.
It caused a number of incidents on what was already a wet morning in Hawke's Bay.
Police were called to a low-impact crash at the intersection of Peel St and Herbert St, (SH2) Waipukurau between 8am and 8.15am.
Two cars collided on a sharp bend on Peel St, several more "spun out". A milk tanker had also hit the kerb earlier in the morning.
Fire communications shift manager Chris Dalton said two fire trucks were at the scene.
While State Highway 2 remained open, a police spokesperson said motorists driving from Waipukurau to Hastings on State Highway 2 should exercise extreme caution.
Peel St was blocked off and lime was being put onto affected areas, including Bogle Brothers Esplanade, and also Pourerere Rd right out to Punawaitai.
Cervus Equipment branch manager Tom Tully was one of the first on the scene at Peel St.
Tully said a staff member heard the initial crash and "the boys went out and as they were there a couple more cars crashed, then the milk tanker came round the corner and its trailer hit the kerb".
"If you go out and stand on the road it's really slippery. We put three utes out with flashing lights, road cones and oil spill signs, then contacted police."
Two crashes also occurred within minutes of each other on State Highway 2 near Te Hauke.
The first, at 8.21am, saw a car crash into a bank on the southbound lane.
Fire and ambulance were notified, and three people with minor injuries were taken to Hawke's Bay Hospital.
A ute is also understood to have hit a bank on the northbound bank, at 8.25am. No one was injured. A tow truck was required.
It is unclear if the diesel spills were to blame for these crashes.
Central Hawke's Bay District Council chief executive Monique Davidson said they were notified of diesel spills in Waipukurau and Waipawa around 8.30am.
"Our roading and stormwater crews met emergency services on site and deployed spill kits to contain the diesel, reduce the impact on our waterways and make the area safe."
She said investigations by the appropriate agencies are under way to identify the source of the spill and, while they do have some leads, these are yet to be confirmed.
"Our priority is the safety of motorists and our environment. Our crews will continue to monitor the area, especially in this wet weather, with additional staff on standby if the need arises.
"We urge people to drive with caution and take care on our roads. If you see or have seen anything that needs reporting, please contact us on 06 857 8060."