The Cambridge fire department swiftly knocked down a smoky rooftop fire at 1 Main St. near Kendall Square, a fire official said.
Cambridge firefighters responded to the call at about noon on the top floor of the 14-story office building. By 12:10 p.m. the fire had been knocked down, Assistant Fire Chief James Burns said in a telephone interview.
Black smoke could be seen billowing from the high-rise building for miles. Local TV station helicopter footage showed firefighters on the roof of the building, where the smoke appeared to be coming out of a cooling unit.
Cambridge police said in tweets that Memorial Drive was open, but Main Street was closed at Third Street, and access to the Longfellow Bridge was closed.
The Oracle University Training Centre and the MIT Technology Review magazine are among the tenants in the building.
A cause has not yet been determined, said Burns.