A home on Johnson Avenue on Thunder Bay's north side suffered some smoke and fire damage after flames broke out in a bedroom around 8:30 a.m.
Six pumper trucks and two aerial platform trucks responded to the fire at a two-storey bungalow.
District Chief Bryan Dychko said the firefighters managed to put out the mattress fire quickly.
"We arrived and we saw smoke coming from the second floor. It was light smoke. We pulled the line, [and] went to the second floor. We were directed to the bedroom, [and] we simply put it out."
Dychko said the bedroom where the fire took place suffered heavy damage. He said an extension cord was near blankets, which appeared to have started the fire.
"It looks like it was electrical. At this time. We had a breaker that was blown downstairs, and there was an extension cord that had tripped a breaker previously. So [we] believe it's electrical."
The two people inside the home were woken up by smoke alarms. No one was injured.