Off the buses ... Brisbane City Council buses at Virginia Bus Depot after a gas tank explosion yesterday morning.

Off the buses ... Brisbane City Council buses at Virginia Bus Depot after a gas tank explosion yesterday morning. 

BRISBANE is facing a back-to-school traffic nightmare tomorrow with half of the city's bus fleet still out of service following an explosion at a bus depot.

Almost 560 gas-powered buses were taken off the road after a gas tank ruptured about 1.15am yesterday. Workers at the Virginia depot were refilling gas cylinders on a bus when the tank exploded, turning into a projectile and striking another bus, the city council said.

No one was injured but all gas-powered buses were immediately taken out of service while investigations were carried out by engineers.

Fifteen high-frequency services, mostly in the northern and western suburbs of Brisbane, were running at a severely reduced rate yesterday, causing major delays for commuters.

More worrying is the hundreds of thousands of Brisbane state school students returning to school tomorrow morning and how a halved bus fleet could affect the road network in such already congested conditions.

A spokesman for lord mayor Graham Quirk said it was unfortunate the incident had occurred so close to the beginning of the school year.

''We're still hopeful that we'll be able to get some of the gas-powered buses out there for Monday but in the meantime we're contingency planning," he said. He said today's timetable would be able to run as normal but only because Sundays used half the bus fleet anyway. A decision would be made today as to whether the gas-powered buses would be put back on the roads tomorrow, he said.

Information on the bus timetables is available on the Translink website.