One resident told the New York Times she received no notification that the building was on fire or any calls to evacuate.
Daniel Nigro, commissioner of the New York City Fire Department, told reporters that the blaze was "a very hard fire, as you can imagine".
FDNY Commissioner Daniel Nigro tweeted at about 8 p.m.: "We found fire on the 50th floor of the building".
Nigro said that despite a "considerable amount of smoke" spreading throughout the building, the structure had "stood up quite well". An alert sent out by the city said the fire was 4 alarms.
The Department of Buildings has issued a partial order to vacate residences 50C and 51C, they note, and residents are able to occupy the 55 floor and above or 45 floor and below.
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Trump Tower is the headquarters of the Trump Organisation, housing residences, offices and stores in a famously opulent gold high-rise. The U.S. Secret Service was made aware of the incident, ABC has learned. Nigro noted that no member of the Trump family was in the 664-foot tower Saturday.
Fire sprinklers were not required in New York City high-rises when Trump Tower was completed in 1983. No concern about firefighter injuries in battling the blaze or two civilians injured by falling debris.
Trump was among the developers who spoke out against the retrofitting as expensive and unnecessary. Mr. Trump and his spouse, Melania, were at Trump International Hotel in Washington, D.C. on Saturday night. "So true Jesse! @WattersWorld", Trump wrote. Trump, the Times reported, called city officials in NY to argue that the sprinkler systems were too expensive-costing up to $4 per square foot and potentially thousands per apartment.
Trump tweeted at 6:42 p.m. that the fire was under control, as he boasted about the building's construction.
The cause of the fire has yet to be determined as well as the identity of the victim.