When the bus was crossing the Welcome Metro station around 11.50 am, when passengers observed smoke in the bus and raised an alarm, police said.
The driver immediately brought the bus to a halt and the 45 passengers who were on board were safely evacuated, said a police officer.
Three fire tenders were rushed to the spot and the fire was doused within half an hour.
The cause of the fire is yet to be ascertained, police said.