The fire department says it's not yet clear what caused Friday's fire. Its tenants include Standard & Poor's and the city Department of Transportation.
In all, 27 people were injured. The firefighter and most others were treated at the scene.
The building's website says it remains without power after Superstorm Sandy. Utilities have largely restored electricity citywide, but some buildings' own equipment was so damaged they're still without power.
The 40-year-old tower on the East River is one of the nation's biggest privately owned office buildings, with 3.8 million square feet of indoor space.