At around 8.20 am the bus on route number 951 between Kamla Market and Pitampura West Enclave was about to pass an intersection beneath a metro flyover when passengers noticed smoke and raised and alarm.
There were around 25 passengers in the bus, including women and children. Some of them suffered minor injuries while trying to get down from the bus, said police.
The entire bus was on fire minutes after the vehicle was vacated by the commuters, said police.
Two fire tenders were rushed to the spot and the fire was doused in around half an hour, after which a cooling operation was launched, said a fire official, adding that the cause of the fire is yet to be ascertained.
Some of the passengers alleged that the fire extinguishers inside the bus failed to work.