The police said that the vandalization could be related to the ongoing labor dispute at the opera house.
"At some point this morning, some administrative offices at the Metropolitan Opera house were vandalized with spray paint," the Met said in a statement. "There was little or no permanent damage. The New York City Police Department is investigating. We have no further comment at this time."
The messages, which were discovered by a maintenance worker, were spray-painted on some paintings and sculptures as as well as on part of a band shell at Lincoln Center.
The Times reports that investigators believe that the vandal has access to the building as the police said there were no signs of a break-in.
Visit metopera.org for more information.