Investigators expect it will take some time to identify a cause of the fire.By Shelby Cassesse

PITTSBURGH (KDKA) — At least four firefighters were injured while battling a four alarm fire on Mt. Oliver Street Sunday evening, according to Pittsburgh Police.

All four firefighters have been taken to a local hospital.

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Two firefighters have shoulder injuries, another is being treated for laceration, and the fourth is being treated for burns.

The call for the fire originally came in at 8:04 p.m. Sunday.

Firefighters discovered a fully involved fire at 38 Mt. Oliver Street, which was particularly active towards the back of the building.

“We went from an offensive interior attack and we transitioned after the interior collapse that trapped a couple of our men,” Pittsburgh Assistant Fire Chief Brian Kokkila said. “Anytime that we have a firefighter injury, especially inside a building, that’s going to cause us to hit the reset button for a second to make sure our crews are safe.”

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(Photo Credit: Shelby Cassesse/KDKA)

The fire was mostly contained to one house but it spread to two adjacent homes on Mt. Oliver Street, and two parts of structures collapsed.

Everyone living in the affected homes was evacuated.

The Salvation Army and American Red Cross were on the scene to assist the affected families.

“Fortunately the firefighters were able to escape serious injury and once again, I have to say the first responders, police, fire and EMS did a superb job with what they were dealing with tonight,” said Pittsburgh Public Safety Director Wendell Hissrich.

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An investigation is ongoing.