WASHINGTON (WUSA) -- One person jumped out of the window of a second-floor apartment in a three-story building, after a two-alarm fire on Thursday evening, fire officials said. 

Four people were injured, including one firefighter, after the blaze on the unit block of K Street, NW, at around 6:00 p.m., firefighters said. 

One of the injured suffered life-threatening injuries, according to firefighters. Two were taken to the hospital with smoke inhalation. The firefighter, who suffered a cut to a hand, "will be fine, " according to fire officials.

The cause of the fire is still under investigation.

The fire has been extinguished. More than 60 firefighters worked on the scene, according to fire officials.