Investigators have determined that arson caused a Monday morning fire on the West Side that injured six people, including a child, according to Chicago police.

The three-story blaze in the Austin neighborhood broke out on the second floor about 5:40 a.m. in the 400 block of South Laramie, according to Chicago Fire Dept. Deputy District Chief Anthony Ellis.

Firefighters responded — about 150 in total — but couldn’t enter the stairwells because they were completely burned out, Ellis said. Several people inside were trapped.

“Initially we had people hanging out the windows,” Ellis said.

One woman jumped from the building to escape the flames before firefighters arrived, Ellis said. A fire department spokesman said she was taken to Mt. Sinai hospital with a sprained ankle.

Since firefighters couldn’t enter the building through the stairs, they used ladders to retrieve people from windows.

One child was rescued from a second-story window, Ellis said. The child was taken in good condition to a hospital.

Five other adults were rescued and transported to hospitals, mostly in serious or good condition, Ellis said. Police did not have an update on their conditions.

A total of ten people were rescued from windows of the burning building, Ellis said.

Chicago police said 28 people were displaced, half of them children.

The fire was limited to second and third floors, and was extinguished by 6:30 a.m., Ellis said.

Chicago police spokesman Tom Ahern said the CPD Arson Unit determined the cause of the fire was arson. Ahern said the investigation was ongoing, and involved were the fire department and U.S. Bureau of Alcohol, Tobacco and Firearms.