Story highlights Trump struck a deal with New York City in 1979 for a major expansion of the now-famous building

But the agreement stipulated that the atrium of the building be kept open to the public for certain times every day

(CNN) The New York City Department of Buildings confirmed Wednesday that it is investigating the use of the Trump Tower atrium for campaign events, which may violate an agreement Donald Trump made to keep parts the building open to the public when he built the landmark.

Department spokesman Joe Soldevere told CNN that the "Department of Building's enforcement unit is investigating whether the atrium was improperly closed to the public."

Soldevere said the probe was sparked by Tuesday's press conference at Trump Tower. Reuters first reported the investigation by the Department of Buildings.

A message left with the Trump campaign was not immediately returned on Wednesday.

Trump struck a deal with New York City in 1979 that allowed for extended zoning of the now-famous building on Fifth Avenue in Manhattan. But the special permit stipulated that the atrium of the building "be accessible and kept open to the public from 8:00 a.m. to 10:00 p.m. daily."

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