A blaze on the same model of bus involved in a spate of fires in Perth two years ago was an "isolated incident", the Public Transport Authority says.
Three Mercedes-Benz OC-500 gas buses went up on flames in late 2012 and early 2013, prompting remedial works on the fleet.
The same model of bus caught fire on Tuesday afternoon at Perth Esplanade Busport, where thick, acrid smoke prompted the evacuation of hundreds of people.
PTA spokesman David Hynes said the latest fire was sparked by a coolant leak.
The bus's fire suppression equipment put out the fire but it reignited shortly after when an electrical system short-circuited.
"These were not the normal circumstances we had some years earlier," Mr Hynes said.
"Last night's incident was a one-off, it was not a systemic problem, in other words it was not a recurrence of the problems we had before."
There are about 470 OC-500 gas buses in Western Australia, making up about one-third of the state fleet, so taking all of the road would have a significant impact, Mr Hynes said.
Each one will be checked on Wednesday for the coolant leak fault as they stop at bus depots.
But the Transport Workers' Union has threatened strike action over the issue.
"Every other bus in the city doesn't seem to do this - it just seems to be the one model," organiser Phil Ogden told 6PR.
"We're very worried. We're talking about not only drivers' safety, but passenger safety as well.
"These buses, they have been an ongoing problem."
In 2014, the PTA agreed to drop legal action against Mercedes-Benz and bus body builder Volgren Australia in exchange for funding works carried out on the entire fleet.
Share
