Chicago building collapse under investigation

CHICAGO -- Crews are investigating the cause of an apartment building collapse on Chicago's South Side.

PHOTOS: Washington Park apartment building collapses

The structure came crashing down near 58th Street and Calumet Avenue in the city's Washington Park neighborhood around 7 p.m. Sunday.

Two women, ages 51 and 78, were trapped in the debris. First responders were able to get them out quickly. A dog was also pulled to safety. The 51-year-old was taken to University of Chicago Medical Center in serious condition and the 78-year-old was taken to Stroger Hospital in critical condition. Their conditions stabilized by Monday morning.

Crews are expected to continue sifting through the wreckage on Monday to make sure there was no one else in the four-flat when it came down. There are four separate apartments in the building, which was built three years ago. But the two women were believed to be the only ones inside at the time of the collapse.

"From what we gather, those were the only two people - besides a dog - in the building," said Chief of Special Operations Michael Fox, Chicago Fire Department.

Inspectors are trying to determine whether the building was leveled by an explosion or if it simply collapsed. Neighbors describe hearing a loud boom and said the building came down fast.

"I heard a loud, sonic boom. The lights went out. My whole house lit up on the inside. I stay on the third floor," said Tryus Lester.

Carl Jones, 17, spent the night trying to sleep in a car holding his frightened dog. His family lives on the third floor of a building adjacent to the one that came down.

"Well, when I heard a boom, like, we felt a little shake. And the window, our window, it blew in and then it came back out," he said.

Jones and others in the neighborhood walked outside to find a cloud of smoke had overtaken the street. It eventually cleared to reveal a giant pile of debris.

"As old as I am, you don't be shocked. You don't be scared. You want to get out of wherever the area is, you know?" said Ernest Thomas.

Peoples Gas officials were also on the scene to determine whether there was a gas leak.