DETROIT (AP) — About a dozen people have been injured, including six children, following an apparent explosion and fire Monday morning at a 2-story apartment building in Detroit.

The explosion was reported about 4 a.m., according to fire officials.

When firefighters arrived, some people were in windows of the building “kind of hanging off ready to jump,” Fire Commissioner Chuck Simms told reporters, adding that they were rescued by firefighters. “Without their fast response and fast thinking this could have been a lot worse.”

Three of those injured were in the same apartment and suffered critical burns, Simms said.

The 12-unit building had a firewall between a section containing eight apartments and a section with four apartments. The apparent explosion occurred on the side with the eight apartments, the fire department said.

Overhead thermal imaging drones were used to confirm the building was empty after the fire was extinguished. Demolition of the building was expected to start Monday to help investigators determine a cause.

Ashley Ridner, her boyfriend and their 5-month-old son were among those rescued.

“It sounded like a bomb,” Ridner told WDIV-TV.

Ridner said her feet were injured while escaping the building through a window. Her boyfriend’s arm was hurt, she said.