A Chicago Fire Department firefighter was injured in a Gage Park warehouse blaze Friday morning on the Southwest Side.Firefighters responded to the fire around 7:10 a.m. at 5653 S. Kedzie Ave., and it was extinguished by 8:35 a.m., according to the fire department in a post on X, formerly known as Twitter. Crews extinguished the blaze from inside the 2-story brick warehouse containing paper products and building supplies, fire department spokesman Larry Langford said.The firefighter was battling flames when he was hurt. It wasn’t clear immediately how he was injured, Langford said, adding he wasn’t burned or trapped.The firefighter remains at Advocate Christ Medical Center in Oak Lawn where his condition, initially described as critical, had “stabilized,” said Langford, who added: “There is no threat to his life.”The firefighter, who was "conscious and alert” when paramedics began treating him, was the only person injured in the fire, which did not spread, and the building remains intact. “You wouldn’t even know a fire happened there if you drove by,” Langford said.It wasn’t immediately known if anyone was inside at the time the fire broke out, and the cause and origin of the fire are under investigation.