Smoke was seen billowing from a vacant home Tuesday at 238 Sumner St.
Neighbors called Oberlin firefighters around 1 p.m. At the scene, they found an abandoned structure with boarded windows. The front door was unlocked.
Inside, a mattress was smoldering.
Oberlin police, paramedics from the Central Lorain County Ambulance District, and firefighters from Wellington and Carlisle Township also responded.
Oberlin fire chief Bob Hanmer said he is unsure what caused the fire, but it must be an emission source because there is no electricity to the house.
According to police, one person enters the vacant building sporadically.