Firefighters say a blaze that burst through windows in a Manhattan apartment building sent 45 people to hospitals, 30 of them firefighters.

The Fire Department says two civilians have life-threatening injuries, and a third is seriously hurt. All the other victims' injuries are considered minor.

Investigators are working to determine what started the three-alarm blaze Thursday evening. It began on the third floor of a 26-story apartment building on Grand Street, on the Lower East Side.

Firefighters and residents say dense, black smoke seeped through the building, making it hard to breathe. FDNY Deputy Chief James Daley says two firefighters became disoriented in a burning apartment, but they were able to escape.

Besides the people taken to hospitals, two other civilians were hurt but declined treatment.

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