Norwalk firefighters extinguished a blaze at a vacant house at 3 Olean Street on Friday afternoon.
According to a report from the Norwalk Fire Department, crews responded to a 911 call at about 3:27 p.m. and within four minutes arrived to find the first floor of the house on fire.
Crews made an aggressive attack of the fire and searched the structure to confirm that no one was inside, according to the report.
The 25 firefighters who responded got the blaze under control within 17 minutes, the report states. Three engines and two fire trucks were dispatched.
The Fire Marshall Division is reportedly investigating the cause of the fire.