CHICAGO (STMW) — A fire at a three-story building sent two men to the hospital, including one who jumped out of a window, early Thursday in the South Side Chatham neighborhood.

The fire started about 1:40 a.m. in a three-story residential building in the 8200 block of South Ingleside Avenue, police News Affairs Officer Jose Estrada said.

The cause of the fire remains under investigation, but it started in a stairwell, Fire Media Affairs Director Larry Langford said.

“Whenever you have a stairwell fire in the middle of the night where there’s nothing that would start by itself, that lends itself to being suspicious,” Langford said. He could not immediately say whether accelerant was found at the scene.

A 55-year-old man jumped from a window on the building’s second floor and injured his back and leg, Estrada said. He was taken to John H. Stroger Jr. Hospital of Cook County.

Another man, 45, had burns to one foot and was taken to Jackson Park Hospital and Medical Center, Estrada said.

Their conditions were not known Thursday morning.

The Police Department was not notified of any displacements from the fire, Estrada said.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2014. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)