A nine-alarm fire that started in the basement of a brick brownstone in the Back Bay neighborhood in Boston has left about 18 people injured, including several firefighters. The cause of the fire is still being investigated.

The Boston Emergency Medical Services tweeted that 18 people had to be taken to nearby hospitals. CNN reports that Steve MacDonald, Boston Fire Department spokesman, said that the large blaze required the response of over 20 fire trucks and 150 firefighters.

While authorities are still trying checking on the status of all the firefighters that were called to the scene, at least three suffered injuries, with one considered serious.

College students who lived in nearby dorms said they could smell a fire, even through closed windows. A Commonwealth Avenue dorm resident, Kayla DaSilvia spoke with the Boston Globe and said, "When we first got to the fire, thick black smoke was coming from that roof. About 15 minutes later, all of a sudden the smoke got really, really black."

The 19-year-old then said she saw some firefighters trying to help another into an ambulance. "They were doing compressions on him."

Gilad Haas, a resident of the neighborhood, claims that he saw and heard an explosion as firefighters were dealing with the blaze. "It was a burst, and then I saw the flames go up. It was definitely scary."