A teenager raised the alarm after noticing that her plastic tote bag was melting.
Ruby Elvin from Bristol said she realised something was wrong when the bag began to droop and smoke started billowing around her feet as she sat on the downstairs back seat on a First bus on her way home from college.
The 17-year-old, who said she normally chooses that seat on top of the engine because it’s warm, raced down to the front of the bus and warned the driver, Bristol Post reported.
A couple of minutes later and the bus was engulfed in a fireball that caused a bang heard a mile away.
Ruby was returning home from morning lectures at the City of Bristol College campus at around 12.40pm today when she realised the engine she was sat on top of was on fire.
She said: “It started getting really hot. My bag started burning up, melting.
"It’s one of those plasticky tote bags and the corner of it just melted.
"Then there was smoke around my feet."
Ruby said: “I ran down to the front of the bus as we were going up the hill into Bedminster Down and told the driver.
"At first she said ‘no, it’s not on fire’, but then she looked round and the back of the bus was filled with smoke.
“I normally sit in that seat at the back of the bus downstairs because it’s on the engine and always warm, and I don’t like being cold.
"This time it was too hot.
"The driver stopped the bus in the road and came out of the cab and told everyone to get out quickly.
"There was maybe six passengers including me downstairs and another couple upstairs.
"We got out, and the driver kept telling us to move further away.
“As soon as we got out we could see that the whole of the back of the bus outside was on fire.
"Really quickly, the flames just literally engulfed it all, where I was sitting and the whole back end of the bus,” she added.
Ruby has remained modest despite many people suggesting online that she is a hero.
She added: “I wouldn’t say that, really. It was the normal thing to do - there was a thick cloud of smoke so I had to do something."
Ruby and the rest of the passengers had to walk the rest of their journey into south west Bristol.
The fire broke out on the number 75 service First Bus in Bristol on Thursday lunchtime.
A First Bus spokesperson confirmed there were no casualties in the incident.
The spokesman said: "We can confirm that there was a fire on the 75 service at Bishopsworth Road in Bedminster Down at approximately 11.55 this morning.
"Passengers were quickly and safely evacuated by the driver and there were no injuries. The fire service was in attendance.
"A full investigation into the cause of the incident will be carried out. “
