UPDATED: 1.37pm:
Police has confirmed that State Highway 2 between Katikati and Tauranga has reopened.
UPDATED 12.50pm:
Re-opening of SH2 is taking slightly longer than anticipated, say police. One part of the truck is still to be loaded onto a recovery vehicle. The road between Katikati and Tauranga is still closed but should be re-opened soon.
UPDATED 11.40am:
SH2 near Whakamarama is expected to be re-open within an hour.
Motorists are still advised to avoid the area.
UPDATED 9.58am:
A reporter at the scene of the accident said a crane has just arrived to lift the truck.
It is expected it will take several more hours before the road is cleared and ready to re-open.
UPDATED 8.50am:
Fire service communications shift manager Scott Osmond said fire crews at the scene were now cutting through the steel casing that held the gas canisters in the truck's trailer.
"That's going to take between four to six hours."
Mr Osmond said he was no aware of any explosions from the scene, which could have been responsible for three puncture-like holes in the roof of the truck's trailer.
"If there has been anything like that it certainly hasn't been reported to us," Mr Osmond said.
Gas canisters could still be seen lying on the side of the highway this morning.
UPDATED 8.35am:
Further evacuations are possible near the scene of a crash that has closed a major arterial route to Tauranga this morning.
A Tauranga bound carrying gases including acetylene, nitrogen, oxygen and carbon dioxide rolled at the intersection of Wainui South Rd and State Highway 2 at 1.27am today.
Western Bay of Plenty head of road policing Senior Sergeant Ian Campion told the Bay of Plenty Timse further evacuations were possible.
"There were concerns that a number of bottles released gas and some when off the side of the road way," he said.
"They've [New Zealand Fire Service] initially said 24 hours. There may be further evacuations later this morning, once the fire service assesses the scene."
"Crash investigation will be out there later this morning, once the scene is under control and safe," Mr Campion said.
EARLIER:
A truck carrying hazardous substances has rolled and forced people in nearby houses to be evacuated from their homes on State Highway 2 between Whakamarama and Apata this morning.
The driver and a passenger of the truck have minor injuries and have been treated at the scene.
Fire Service shift commander Megan Ruru said the evacuations were a precaution because of arcing powerlines.
The truck was carrying gases including acetylene, nitrogen, oxygen and carbon dioxide.
"It is anticipated that it will take some time. (It) could possibly be up to 24 (hours) to be able to inspect and unload the truck safely," he told Newstalk ZB.
Police have not said how many people were evacuated but said power had been isolated in the area since 4.30am.
The highway has been completely blocked about 8km south of Katikati and traffic is being turned around.
Police said it would take "some time to inspect and unload the truck" and there were no available detours between Tauranga and Katikati.
The alternative for Tauranga traffic is via the Kaimai Range and Matamata.
Motorists are being turned around at the Apata Coolstore.
The road is expected to be closed until 4.00pm this afternoon.