Evanston firefighters unexpectedly put out a house fire early Tuesday in the northern suburb.

At 12:27 a.m., the firefighters were returning from an automatic fire alarm when they smelled something burning in the area of the 2300 block of Ridge Avenue, according to a statement from the Evanston Fire Department.

The firefighters parked and walked around Ridge Avenue, finding a two-story, single-family home with activated smoke detectors and full of smoke, the fire department said. The home was rehabbed and unoccupied.

Crews upgraded the alarm to box level, and several other agencies helped extinguish the blaze within 24 minutes, the fire department said. An Evanston firefighter was treated and released from the hospital for heat exhaustion.

No other injuries were reported.

The cause of the fire is under investigation.