The State Fire Marshal is investigating what caused two antique buses to catch fire in the Oakdale area of Portland overnight Wednesday morning.

Firefighters say they were called to 464 St. John Street at about 3:30 am, where they found two antique buses parked side-by-side on fire, with the blaze spreading to a nearby building.

They say their quick response limited the fire to the outside of the building and there was no structural damage.

The cause is still not known, and follow-up investigations are underway.