At least 8 hospitalized after Chicago apartment building explosion

At least eight people were hospitalized after an explosion inside a building Tuesday on Chicago's West Side, authorities said.

First responders arrived at the scene of a four-story apartment just before 9:30 a.m. and found the top floor of the building had collapsed, Marc Ferman, deputy fire commissioner for the Chicago Fire Department, said at a news conference.

Eight people were hospitalized, including one person "from the building across the street," Ferman said.

Three of the people who were hospitalized were in serious to critical condition, the Chicago Fire Department said. The victims had injuries varying from "burns to traumatic injuries," Ferman said.

Residents were also displaced by the explosion, Ferman said, adding authorities are not sure how many people had been displaced.

Ferman said crews are "confident we got everybody out," and were finished searching for more victims.

A mass casualty emergency medical services unit was dispatched to the scene, along with 10 ambulances, the department said.

The adjacent building was also evacuated after the explosion in Chicago's South Austin neighborhood, the fire department said.

Images and a video posted on social media by the fire department showed firefighters and multiple fire trucks gathering near a street littered with debris. The top floor of a building appeared to be destroyed, according to footage posted by the department.

The fire department did not provide any additional details on injuries or the cause of the explosion.

"Right now, we don't know what caused this incident," Ferman said. "It's still under investigation."

Crews from Peoples Gas, Chicago's natural gas utility provider, were called to the scene, which is "standard procedure," Brendan Conway, spokesperson from Peoples Gas, said in a statement to USA TODAY.

"Our crews have been on the scene helping with the situation but at this point there’s no indication this was related to our equipment or our natural gas service," Conway said.

Chicago Mayor Lori Lightfoot said she is "closely monitoring" the collapse.

"My thoughts are with those who were injured and displaced in the building collapse in the Austin neighborhood," she said in a Tuesday statement.

Contact News Now Reporter Christine Fernando at cfernando@usatoday.com or follow her on Twitter at @christinetfern.

This article originally appeared on USA TODAY: Building explosion in Chicago: 8 injured; cause under investigation