Perth's fleet of compressed natural gas buses will be kept on the road while an inquiry is undertaken into why one of them was destroyed by a dramatic fire on Friday morning.
The Transperth bus caught fire as it was heading south on Rockingham Road in the southern suburb of Munster around 6.30am this morning and was completely burnt out within minutes.
The driver, who was alerted by one of the passengers to the blaze, had attempted to put out the fire with an extinguisher but was unsuccessful.
As the flames took hold, the safety valve on the fuel tank expelled remaining gas rather than allowing it to reach dangerous pressure levels, the Public Transport Authority and Transperth said in a joint statement.
As photos of the dramatic blaze flashed across social media, state Transport Minister Troy Buswell said significant resources were in place to investigate the cause of the fire.
"I have driven buses and the threat of a fire on a bus is a very, very serious matter," Mr Buswell told reporters.
"We will be investigating urgently and with every available resource.
"We need to understand why this fire started and why our onboard systems were not able to deal with it.
"It is incumbent on us to understand what happened and we will do that very quickly. If there are broader safety issues we will act."
In 2011, the union for bus drivers in Sydney announced they were boycotting the fleet's gas-powered buses, saying it had been kept in the dark about a fire on one of the vehicles caused by an explosion, which prompted the NSW Industrial Relations Commission to order drivers back on the road.
And in 2009, several buses in and around Perth were damaged by fire.
Mr Buswell said he still had confidence in the bus fleet and so should the public.
"I do have confidence in the bus fleet, but we need to investigate what happened this morning and if we have to make changes we will," he said.
"There is no evidence that this is happening broadly, or widely. This is the first incident in three years and there are over 500 of these buses in circulation."
Transperth said it had ordered an immediate inspection of the fire-suppression equipment on all of its 550 gas buses, comprising about 43 per cent of the Transperth metro area fleet.
