DELAWARE COUNTY, Pa. (CBS) — Two children had to rescued from a fire that injured four people, including two firefighters, and forced 150 people from their homes at an apartment building in Delaware County.

The three-alarm fire broke out shortly before 8:30 a.m. Monday in the C-building of the Cliff Park Apartment complex in the 300 block of North Sycamore Avenue in Clifton Heights.

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Police said it appeared the blaze started after a child lit a piece of paper on fire, then panicked and threw the paper under the bed.

“We interviewed the family where the fire began in the apartment complex and came to find that a 5-year-old had been playing with a lighter,” said Cliffton Heights Police Chief Tim Rockenbach. “We believe that is going to be the cause of the fire.”

Officials said the flames engulfed the third-floor apartment and two children had to be dropped from a window to safety. Authorities said they appeared to be unharmed, but were taken to the hospital for precaution.

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Authorities said the heavy fire also forced two women to jump from a third-floor window. They were taken to the hospital and treated for what officials said were non-life-threatening injuries.

Officials said two firefighters also sustained minor injuries. They were taken to the hospital where they were treated and released.

Red Cross officials said they were helping 150 people who were displaced by the blaze.