Santa Barbara County firefighters responded to an acute case of irony yesterday when they arrived at the scene of a fiery Clean Air Express bus billowing thick plumes of black smoke into the air.

The passenger bus fire, which was reported a little before 7 a.m. yesterday, closed both southbound lanes of Highway 101 near Los Alamos, but no injuries were reported.

According to Santa Barbara County Fire Dept. spokesman Captain Eli Iskow, the bus’ 28 passengers and driver were off the coach and safe by the time the first of four fire engines arrived to douse the flames. Passengers even managed to help a disabled bus rider safely disembark,[[nix,]] before the trucks arrived.

At the moment, the cause of the fire is unknown. Santa Barbara County Clean Air Express buses – which advertise “stress-free commuting” – run on compressed natural gas. Iskow said the buses usually pose little danger.

“The Clean Air Express buses are run by CNG and pose only a small explosion hazard if the fuel cylinders are exposed to the heat of uncontrolled fire, due to their built-in safety features,” Iskow said.

It took firefighters 15 minutes to knock down the flames once they had ensured all passengers had exited the vehicle, Iskow said. Thus far, the county has yet to estimate the amount of monetary damage caused by the fire.