CHICAGO (AP) — Six people — one of them a firefighter — have been injured in an apartment fire on Chicago's South Side that officials say may have been deliberately set.

None of the injuries from Friday morning's fire were considered life-threatening but Fire Department spokesman Larry Langford says that one of two children injured is listed in serious condition from smoke inhalation.

Langford says that when firefighters arrived shortly after 630 a.m. , they saw people hanging out the windows "threatening to jump." He says firefighters calmed then and then using ladders, rescued at least two dozen residents.

Langford says the state fire marshal was called to the scene after firefighters found evidence of arson at the scene.

Last month, 10 children were killed in another apartment fire in the city.