CHICAGO (CBS) — One Chicago firefighter suffered a minor injury Tuesday morning while helping extinguish an extra-alarm blaze in Englewood.

The fire started around 6:15 a.m. in a vacant building near 70th and May streets.

Deputy Fire Commissioner William Vogt said there was heavy fire in a building marked with a red X, indicating to firefighters that it was too dangerous to go inside.

Flames quickly spread to two neighboring buildings.

Because of the volume of fire, and the dangerous structural conditions, fire officials called in a 2-11 alarm to bring extra trucks and crews to the scene. Vogt said approximately 100 firefighters and 16 pieces of equipment responded to the fire.

About 15 minutes after the first firefighters arrived, two walls of the building where the fire started came down, and the roof collapsed.

As a precaution, a mayday call went out, because a crew of firefighters was working close to the building, and there was a threat someone might have been lost as the wall came down.

Vogt said no one was trapped when the walls collapsed, and only one firefighter was hurt, when a falling brick hit him in the arm. The firefighter was taken to Little Company of Mary Hospital in good condition, with a minor contusion to his arm.

Although the building where the fire started was a total loss, the two neighboring buildings were saved, according to Vogt.

“I can tell you this, the companies did an excellent job recognizing that the structure was unsafe at this time. They did a phenomenal job saving the exposure buildings,” he said.

One neighboring building was vacant. There were four people living in the other building, but they were safely evacuated when firefighters arrived, and were not injured. Vogt said that building had some minor fire damage that would need repairs.

The cause of the fire was under investigation.