An early morning house fire that engulfed a vacant home in Northeast Washington also damaged a neighboring home, officials said Monday.

Firefighters responded to the blaze in the 5800 block of Field Place NE, about a block from the Maryland border, around 4 a.m. The two-story home where the fire originated appeared to be vacant, according to officials.

Authorities believe the fire began outside the house, on the back porch, and spread inside and to the roof. From there, it appears the fire spread to a neighboring home, which was occupied.

The occupants of the neighboring home were unharmed, but both structures were badly damaged, officials said. No injuries have been reported.

The cause of the fire remains unknown and authorities do not know who or what may have set the blaze. The incident remains under investigation.

Because of the fire’s proximity to Eastern Avenue, a main thoroughfare along the D.C.-Prince George’s County border, officials warned that there may be some traffic delays this morning. Drivers are advised to leave extra time during their commute or to avoid the area.