(Updates with additional firefighter heard, quotes from fire official)
BOSTON, March 26 (Reuters) - At least three Boston firefighters were injured, one seriously, on Wednesday when a fire broke out in a four-story building in the city's historic Back Bay neighborhood, drawing a large-scale emergency response, local officials said.
All residents of the apartment building escaped unharmed, said Boston Fire Department spokesman Steve MacDonald. He described the blaze as a nine-alarm incident, the department's highest level of severity, with more than 150 firefighters at the scene.
"The fire right now is still not out. It is still raging from the inside," MacDonald told reporters. "It's a very unstable condition right now with the flames that are through the roof, and it's hard fighting it from the outside."
Of the three firefighters brought to area hospitals, one was listed in serious condition while the injuries to the other two were not believed to be life-threatening, MacDonald said.
Firefighters were focused on keeping the blaze from spreading to neighboring buildings on a day the city was buffeted by high winds, MacDonald said.
Live television video showed an enormous plume of smoke rising from the building, and hovering over the city. State police said they closed a major roadway along the Charles River behind the burning building.
(Reporting by Scott Malone; editing by Gunna Dickson)