CHICAGO (CBS) — Firefighters rescued seven people who were trapped on the second floor of a Montclare neighborhood apartment building, after a heavy fire started burning overnight.

CBS 2’s Susanna Song reports a firefighter suffered minor injuries while at the scene of the blaze, but no one inside the building was seriously hurt.

Firefighters responded to the fire at a three-story building at 3009 N. Harlem Av. around 12:30 a.m., to find several people hanging out second floor windows, shouting for help.

“You could see fire blowing out of the window. You could see fire blowing and the smoke intensity rising up through the building – which it does, like a vertical shaft – and the people up on the second floor were hanging out the windows, yelling that a lot of smoke was in their apartment, and how were they going to get out,” Fire Battalion Chief David Dietz said.

Crews rescued seven people who were trapped on the second floor, due to heavy flames and smoke from the blaze.

Ricardo Flores, of Arkansas, said he was visiting his parents, and the family was asleep when they smelled smoke in their second floor apartment.

“There was real bad smoke. My father came and woke us up. We were asleep,” he said. “The fire was very intense, so the Fire Department told us to come out through the back, but the flames were too bad, so we went to the front door, and the flames were bad as well, so they had to clear a way. They had to clear the fire out for us to get out.”

Firefighters put the flames out within 30 minutes.

Six people were treated at the scene after they were rescued, but declined to be taken to a hospital.

A firefighter fell and hit his head while at the scene, but was listed in good condition.

The cause of the fire was under investigation.

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