Bus Eireann says all passengers on board one of their coaches which caught fire last night in Letterkenny were safely evacuated before the blaze broke out.
The Expressway service was en route from Letterkenny to Dublin when it became engulfed in flames at around 8:30pm at the Dry Arch Roundabout.
15 passengers were on board at the time.
Bus Eireann's Expressway 32 service passes through Emyvale, Monaghan Town, Carrickmacross and Castleblaney.
The fire service battled to bring the blaze under control while Gardaí managed traffic in the area.
Bus Eireann says the incident was an exceptionally rare occurrence and has confirmed a thorough investigation will be conducted.
Passengers were accommodated to continue their journey to Dublin on another vehicle.