The engine of a public bus exploded and burst into "two metre high" flames while driving in a busy street in Sydney's Surry Hills on Monday evening.
Transport for NSW confirmed the gas-powered bus, operating on route 394 from La Perouse to the City, caught fire around 7.30pm on Monday, on Flinders Street at South Dowling Street.
The bus was safely evacuated, and no passengers were injured.
Pictures posted on Twitter by Surry Hills resident Phil Dye show large plumes of grey smoke rising from the bus, which was stopped in the bus lane with its doors open, "20 seconds after the explosion ... before it caught fire".
"As I was watching and starting to take a photo, the bus sort of exploded more at the back and the flames started to leap out," he told the ABC.
"No-one was going near the thing, I can tell you, the smoke was extreme and the flames were probably about two metres high from the back of the bus," Mr Dye told the ABC.
The fire brigade attended the scene quickly and extinguished the fire.
Bus explodes and on fire in Surry Hills. No passengers it seems. #smh #abcnetau #surryhills pic.twitter.com/qMbJQ9K1lF??? Phil Dye (@dye_phil) November 27, 2017
The incident comes a year after a bus burst into flames on the Sydney Harbour Bridge during peak hour traffic, requiring three people to be taken to hospital.
After investigations last year, Transport NSW found the Harbour Bridge bus fire started due to an electrical malfunction in the engine bay at the back of the vehicle, prompting many to call for greater fire safety regulations of public buses.
Transport NSW confirmed that all state and private buses were installed with engine fire suppression units by August this year, with all new buses also fitted with the same systems.
This included the bus which caught on fire on Monday.
A spokeswoman for Transport NSW said the fire suppression systems are "not designed to prevent fires, but allow people on the bus more time to escape in the event a fire does occur".
The Office of Transport Safety Investigation will inspect the bus on Tuesday to determine the cause of the fire, and will conduct an investigation with Transport NSW.
