STAGECOACH has reassured passengers of their safety after another of its hybrid buses was engulfed in flames.

Drivers were stuck in standstill queues for two hours on the Oxford ring road on Wednesday night, watching in horror as a raging fire consumed the double-decker.

The fire happened on the Eastern Bypass, in almost exactly the same spot as a fire on another of its hybrid buses in May 2017.

In both cases, there were no passengers on board and the drivers escaped uninjured.

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Chris Coleman, managing director of Stagecoach in Oxfordshire, said: "This is an isolated incident and safety is always our priority.

"We are working with the authorities and helping them with their investigation.

"The Stagecoach bus involved was not in service and no passengers were on board at the time."

Oxfordshire Fire and Rescue Service confirmed yesterday that the cause of the fire is still under investigation.

Some concerns have been raised nationally about the potential fire risk posed by electric and hybrid vehicles.

Official guidance from the Health and Safety Executive online states: "Electric and hybrid vehicles introduce hazards into the workplace in addition to those normally associated with the repair and maintenance of vehicles, roadside recovery and other vehicle related activities.

"These include the storage of electrical energy with the potential to cause explosion or fire."

Commenting on the Oxford Mail's Facebook page, one reader said: "They have had nothing but trouble with theses new buses...breaking down and now, catching fire!"

Another added: "Wow, another hybrid gone up."

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Plumes of black smoke choked the air as the fire took hold at about 8pm, with footage recording the sound of loud crackling and popping as the windows shattered.

Drivers abandoned their cars to get to safety, before being instructed by police to get back inside as the clouds of smoke grew.

The fire happened on the northbound side, just past the Mini plant, and the road did not completely reopen until 10pm.

One witness, who works at Angel Sharp Media, told the Oxford Mail: "We were driving along and could smell something weird.

"The bus looked like the engine was overheating or just had some steam coming from it, but the smell was strange - it pulled over with its hazards on.

"Both lanes of traffic stopped and we started reversing as we realised something more serious was up."

The witness, who asked not to be named, said the bus driver got out and ran to the other side of the road.

Police arrived on scene quickly and initially closed off both sides of the road due to the poor visibility.

The witness added: "It was very dramatic - oncoming cars were driving through huge clouds of smoke with their headlights lighting the flames and smoke up.

"The small flames started inside the bus in the middle, then they started growing. We couldn't quite believe it.

"Then the back window smashed with a loud noise, and flames started pouring out of the windows."

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Fire crews from Oxford and Wheatley were sent to douse the flames, which took about half an hour to get under control.

The surrounding area was severely congested as people tried to avoid the standstill traffic.

Photos of the aftermath showed the blackened wreckage of the burnt-out bus, which was loaded onto a recovery van and taken away from the scene.

Stagecoach launched a fleet of electric hybrid buses in Oxford in 2010, and the city became the first outside of London to pioneer the greener technology on a large scale.

The fleet was initially rolled out with 26 double-deckers in a project costing £7.5m. Under the plan for a Zero Emission Zone (ZEZ) in Oxford, councils have ambitions for all buses in the city to run with zero emissions by 2030.

Councils have secured £2.3m in government funding towards electric and low-emission buses, according to the latest ZEZ document.

Well-known electric car maker Tesla has previously dismissed concerns about fires, claiming fuel-powered cars are 11 times more likely to catch fire.