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.