A fast-moving house fire on Harriet Street sent one resident to the hospital with severe burns early Thursday as Norwalk firefighters mounted an aggressive response.

Crews were called to 39 Harriet Street at 4:36 a.m. and arrived to find heavy fire pouring from the second floor of the 1.5-story home.

Firefighters say they knocked down the flames within 19 minutes using an interior attack from the first-alarm assignment, while a second-alarm crew staged nearby.

In total, 39 firefighters responded, including four engines, two ladder companies, a rescue unit, and command staff.

Two residents—one from each floor—were able to escape before crews entered the home. The second-floor occupant was taken to the Bridgeport Hospital Burn Center with severe injuries, while the first-floor resident was unhurt and assisted by the Red Cross. Two firefighters sustained minor burn injuries.

Norwalk Hospital paramedics responded with five medical personnel, and fire departments from Westport and New Canaan provided station coverage during the incident. The Norwalk Fire Marshal’s Office is investigating the cause of the fire.