NBC New York reports that the two workers have been secured using ropes, and emergency workers are trying to find a way of winching them to safety.
Parts of the streets below, on 57th and 58th streets and Eighth Avenue, have been closed off.
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Levels of safety are not high enough in prisons, meaning that reform of inmates cannot take place, Prisons Minister Sam Gyimah has said.
The Government's Prevent campaign is "simply not trusted" by many British Muslims, the Independent Reviewer of Terrorism Legislation said.
The former Labour minister criticised the government's approach to leaving the European Union.