PITTSBURGH (KDKA) — Three firefighters were injured while fighting a three-alarm fire on Madiera Street overnight.

The fire started as a two-alarm fire at 11:25 p.m. on Friday. Heavy flames were seen from the second floor of the residence on fire, according to Public Safety.

One firefighter fell 10 feet off a ladder and injured his head. Medics treated him at the scene, and he was conscious at the time before he was transported to a local hospital. Another firefighter fell through a hole in the residence’s floor and twisted his back. Medics also took him to a local hospital. A third firefighter suffered extreme heat exposure and was treated at the scene.

Firefighters put the fire under control just before 12:25 a.m. Saturday. The Fire Investigation Unit is investigating what caused the fire.