Alternative fuels like compressed natural gas (CNG) are an easy way to make ICE-powered buses – and passenger cars – less harmful to the environment. However, in the extremely rare case something goes wrong with the tanks, things can turn pretty ugly. This is exactly what happened on April 16 near the Italian city of Perugia, with a city bus bursting into fire. The flames coming out of the roof looked like a scene from a space launch program or a CGI effect, although the video is legit.

Starting with the positive, no one was harmed, since there were no passengers on board and the mechanic who was driving the bus got out on time, closely avoiding the flames. According to local media, he was the one who called for help, but due to the extent of the fire, when the firefighters arrived at the scene it was already too late.

Watch Also: Electric Bus In China Erupts In Fire That Spreads To Four Others

Predictably, the video of the fire-gushing bus quickly became viral on Facebook and Twitter. Some users mistakenly stated it was an EV while others said it is an FCEV with the hydrogen tanks on the roof. However, a closer look reveals it is an Irisbus Iveco Cityclass with a regular internal combustion engine and CNG tanks mounted on the roof.

This is the standard layout of such vehicles with many of them still operating in European countries including Italy and Greece. CNG-powered buses are used as a cleaner alternative to the traditional diesel-powered ones without the drawbacks of electric vehicles in terms of the available range and long charging times. While this is not the first time a CNG-powered bus turns into a flamethrower – a similar accident occurred in the Netherlands back in 2012 –  it is extremely rare.

The source of the fire was unknown, and we don’t know how did it reach the gas tanks on the roof. From the looks of it, the pressure-reducing valves are doing their job allowing for the fuel to burn without exploding. Still, if this thing happened in a crowded urban environment, the fire could easily expand to the surrounding vehicles and premises. A second video uploaded on YouTube shows the aftermath with the remains of the bus. The temperature was so high that melted the asphalt around the vehicle and started a fire in the nearby fields.