Updated 11/24/14 – 11:07 a.m.

(CBS) — Two women and a dog were rescued from the rubble of a collapsed residential building Sunday night in the Washington Park neighborhood.

Firefighters swarmed the property at 58th Street and Calumet Avenue around 7 p.m. after reports of an explosion, and they pulled two women from the flattened property.

Fire Department spokesman Larry Langford said the women did not have any visible injuries when they were rescued.

A 78-year-old woman who lived on the second floor was listed in critical condition when she was taken to John H. Stroger Jr. Hospital of Cook County, because of the possibility of internal injuries. However, she was alert and talking when she was pulled out of the rubble.

A 51-year-old woman living on the third floor was in fair-to-serious condition when she was taken to the University of Chicago Medical Center.

Firefighters also rescued a dog named Tigger.

The building was only a few years old when it collapsed. Neighbors who heard and saw the building come down couldn’t believe their eyes.

Angela Brooks said it sounded like a transformer blew around 7 p.m. When she looked out the window, the building was leveled. Her car was crushed by falling debris.

“My bed moved, so it was a pretty strong explosion. I immediately went to the window to look outside, because I knew it came from the northern direction,” she said. “You couldn’t see anything, because it was smoke. So after about five minutes, I looked out, and I saw, one, my car was totaled; and then, two, I saw the building next door was completely gone.”

Angela Brooks' car was crushed by falling debris when an apartment building in Washington Park collapsed Sunday night. (Credit: Angela Brooks)

Angela Brooks’ car was crushed by falling debris when an apartment building in Washington Park collapsed Sunday night. (Credit: Angela Brooks)

Crews continued searching the rubble through the night, in case others were trapped, though police and fire officials said they don’t believe anyone else was in the building.

Investigators have not yet determined what caused the building to fall.

“We’re not sure if it was an explosion or just a collapse,” Fire Chief Michael Fox said. “As we dig through, hopefully we’ll be able to find out more of what caused it.”

The three-story brick building was only a few years old when it came down. Langford said it might have been a natural gas leak, or a structural problem.

“We also heard from some people here last night that some remodeling was being done, that the basement was being gutted out. So, I don’t want to speculate too much, but that’s where the supporting load-bearing walls are. So we don’t know what was going on in the building, yet. That’s part of the investigation,” Langford said.

Until authorities determine what caused the building to collapse, tenants of the two buildings on either side have been told to stay out.