The incident happened during an intermission of Guillaume Tell, prompting anti-terror units to enter the Lincoln Center venue.
Some of those attending said a man told them he was there to release the ashes of a friend, police said.
The man has been identified and the authorities are trying to reach him.
Cultural venues in New York are on alert for potential threats following the 9/11 attacks and the sprinkling of the unknown material caused the opera house to be evacuated.
The show was canceled, as was the night’s performance of L’Italiana in Algeri, while police investigated.
John Miller, the New York Police Department’s deputy commissioner in charge of intelligence and counterterrorism, said that while disposing of ashes may violate city codes: “I don’t believe at this point that we see any criminal intent here.”
Some of those attending said they were particularly sad to miss the fourth act of Guillaume Tell, which is considered to have the best music in the opera.
Image source: Wikimedia Commons President-elect Donald Trump celebrated his election victory at the Ultimate Fighting…
Millions of voters across the US chose to return Donald Trump to the White House…
Donald Trump declares victory in the US election as he addresses jubilant supporters in Florida.…
Stocks around the world are rising as Donald Trump appears to be on the cusp…
Donald Trump has won Pennsylvania, North Carolina and Georgia and taken a lead over Kamala…
Quincy Jones, the celebrated musician and producer who worked with Michael Jackson, Frank Sinatra, Ray…