A city bus operating on compressed natural gas (CNG) caught fire at about 11 a.m. due to a failure of the cooling fan’s drive motor. The driver was able to evacuate all the passengers, attempted to put out the fire and then move the bus to a safe location. The heat from the fire triggered the safety system on the CNG’s composite cylinders, causing the gas to be released laterally and thus spewing out flames, over a distance of 15 m, perpendicular to the direction of traffic. The direction of the flaming jet was contrary to the safety objectives defined in the best practices, which recommend orienting the thermal fuse openings in an upward direction. The fire brigade was able to put out the fire after the CNG had been completely released. The public transportation company inspected all of its vehicles.