Update, 3:47 p.m.: A spokesperson for Montgomery County Fire and Rescue Services confirms that the bus was a Ride-On bus.

"The bus itself, according to the bus driver, was out of service at the time of the fire, meaning there were no passengers on board," said Capt. Oscar Garcia. The driver told firefighters he was on his way to the bus depot when the engine caught fire.

Washington Examiner reports that three other Ride-On buses have "burst into flames" since September 2010.  

Original story, 8:46 a.m.: The engine compartment of an unidentified bus caught fire in White Oak Tuesday morning, according to Montgomery County Fire and Rescue Services.

Capt. Oscar Garcia, spokesperson for the department, said firefighters were called around 7:42 a.m. to the intersection of Oak Leaf Drive and Columbia Pike. All of the passengers were off of the bus when fire crews arrived and no one was injured, he said. 

Garcia was not able to confirm the type of bus or how many people were traveling on it.