Eight people were rushed to hospitals after being injured when an explosion Tuesday tore through the top floor of a Chicago apartment building, officials said.

The explosion at the 36-unit, four-story apartment building in the South Austin neighborhood occurred at about 9 a.m., officials said. Chicago Fire Department Deputy Chief Marc Ferman told reporters a few hours later that the department had finished searching for potential victims and was “confident” that nobody remained trapped inside the building, of which much of the top floor had collapsed.

He said technical crews had shored up the upper floors to allow firefighters to search “to make sure we didn’t leave any victims underneath any of the debris.”

A cause of the blast had not yet been determined.

Seven of the injured were in the building on the city’s West Side when the explosion occurred and one apparently was in a building across the street, Ferman said. Three of the people who were hurt had serious to critical injuries, the department said.

Photographs and video posted on the Chicago Fire Department’s Twitter page showed that much of the top floor was destroyed. Scores of bricks and other debris had fallen onto the street, crushing at least one car and seriously damaging two others.

Several residents said they were home when the explosion rocked the building.

“I was asleep, and all of a sudden there was a loud booming,” Lawrence Lewis, who was asleep at the time, told WGN television. “I woke up to my windows gone, my front door blown open. I just saw smoke, and I ran out of the house. I was asleep. I’m shook up right now.”

Otis Maning, who lives across the street, told the Chicago Sun-Times that he was on his couch watching television when “all of a sudden I hear, `Boom!’”

“My heart almost shot out of my body. … I saw windows busted open, I saw debris,” he added.

Yumika Bady, 25, was also at her home across the street and saw that the blast blew out the back window of her car that was parked nearby.

“It just made my apartment shake,” Bady told The Associated Press.

Chicago police bomb squad and agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives also responded to the explosion.

(AP)