At least eight people were injured in an explosion which occurred in Waukegan, Ill., a suburban Chicago plaza on Thursday probably caused by a gas leap, according to fire officials.

The injured people were taken to Vista East Medical Center and treated for non-life threatening injuries. According to hospital spokesman Adam Beeson, four of them were released by Thursday afternoon.

Deputy Fire Chief Dan Young said that three people were treated at the site of the blast.

Authorities think that the explosion was caused by a gas explosion, and some of the shop owners said that for some days they had smelled gas.

Young said that he was "99.99 percent" sure that there wasn’t anyone left in the rubble.

He said: "The whole back of the building was pancaked," the Associated Press reports.  

The explosion occurred around noon in the business district about 40 miles north of Chicago. Windows and the roof of the plaza collapsed due the blast. The plaza housed a cell phone shop, a tuxedo store, a hair salon and other business.

Magdi Hussein, 29,  of Chicago, working at a store across the street from the plaza said: “It felt like someone threw a bomb in the middle of the block. It shook the whole block. You could feel the store shaking,” the New York Times reports.

Candi Rixie working at Leno's Submarine Shop, a block from the plaza said that it felt like an earthquake, like the building was hit by a car.

As she rushed out of the restaurant along with others they mistook the mannequins from a shop as bodies. The mannequins were thrown in the street by the blast.

Gary Podyma, who took the inventory at the Living Foods Pantry health food store across the street from the blast, saw a big cloud coming towards him.

He said: "To see a building coming toward you like that — words can't describe the feeling you get. It was frightening, it was ominous."

He said that after the explosion he could smell a strong odor of gas.

“It's amazing that anybody survived,” Podyma said.

By Thursday evening the exact location of the explosion was not determined due to the damage to the building.