The FDNY and NYPD responded to Lincoln Center shortly after 5:20 p.m. Saturday during the performance of "Guillaume Tell."
At an afternoon press conference, the NYPD said multiple witnesses told them that the man who sprinkled the substance was from out of town and indicated that he wanted to sprinkle the ashes of his mentor during the performance.
As a safety precaution, the Met canceled the remainder of the performance. In addition, Saturday night's performance of "L'Italiana in Algeri" was also canceled. However, police later said that they do not believe the man had any criminal intent and may not believe he has done anything wrong.
Met Opera General Manager Peter Gelb said that none of the musicians were hit by the ashes and that the Opera will be open for business on Monday. He also added that the organization hopes people will continue to come to the opera, but will "leave their ashes at home."
A Met representative at first announced that a technical issue was causing the delay, then returned a few minutes later to announce that the fourth act would not be performed. The audience was told to go home.
"Everybody kind of slowly walked out," said Dylan Hayden, of Toronto. "As we were exiting the building, I noticed the counter terrorism unit going into the building."
No one was injured. An audience member says the evacuation of the opera house was calm.
The Associated Press contributed to this report.