A natural gas leak that led to the partial evacuation of Kamo was caused by a driver-less bus rolling 50m backwards after its handbrake was left off.
The out-of-control CityLink bus rolled across Kamo Rd, onto the forecourt of Z Energy service station and into a cage containing gas pipes. It narrowly missed street signs, petrol pumps and poles bearing the Z Energy forecourt roof.
The bus driver had left the vehicle about 7.30am to buy a newspaper from Kamo Dairy near Grant St, as he does every morning, the dairy owner said.
When he turned around the bus was gone.
"He said to me, 'My God, someone stole my bus."'
The bus was parked at the Kamo Rd bus stop opposite the dairy, and its handbrake had been left off.
The commotion at the service station led the driver to the scene where his Tikipunga route CityLink bus had crashed in to gas pipes behind a cage.
Z Energy staff immediately evacuated the site and called 111, as did nearby residents who heard the loud crash.
Ten fire trucks were brought in, firefighters working to clear the gas and contain the leak. About 20 police officers were at the scene, at cordons and evacuation centres working alongside Civil Defence officers.
Z Energy senior communications officer Sheena Thomas said it was miraculous that no one was injured and no more damage was done.
Whangarei senior station officer Ron Wilson said the bus collided with a pipe that was part of the city distribution of natural gas.
"The bus has bent the main pipe which is an 18mm pipe under high pressure. It has also broken a relief valve," Mr Wilson said.
Gas leaked from the pipe, causing a gas cloud that sat above Wilkinson Ave in Kamo.
Mr Wilson said it was very lucky it did not ignite.
While emergency services had earlier thought the leak was from a liquefied petroleum gas (LPG) tank, which has a 1km radius destruction zone risk, the bus collided with a natural gas pipe.
Mr Wilson said that in the worst case scenario, had the leak been ignited, the natural gas pipe would only have emitted a high flame or flare. The high pressure pipe is part of the city's natural gas network.
A 600m cordon was in place round the southern side of the service station.
Firefighters worked with water hoses to absorb the gas and disperse it.
The owner of the gas reticulation centre, Vector, worked to close valves and redirect the gas through a different part of the system, which was confirmed at about 9am.
Mr Wilson said the conditions were near perfect to deal with the incident, saying if it happened later in the morning with schoolkids around and more traffic, it would have been more difficult to contain.
Kamo business owner Tim Langman saw the accident happen. He arrived at his business, Bin Inn, directly opposite Z on Wakelin St, at 7.20am, to open the shop for 8am.
"We turned up and I heard a noise - a bus was going backwards through the Shell [Z]. There was no driver in it - it had rolled away," he said.
The cordons were lifted, businesses opened, and school started by 9.15am.
Director of Ritchies buses, owner of CityLink buses, Andrew Ritchie said the company felt fortunate that there was not a bigger disaster yesterday, and they were going through the appropriate process with the driver.
Whangarei/Kaipara Area Commander Inspector Tracy Phillips said an accident investigation was under way, and road policing officers were following up to see if any charges will be laid against the driver.