New York's Metropolitan Opera stopped a performance on Saturday after someone sprinkled an unknown powder into the orchestra pit.

Sam Neuman, a spokesman for the Met, said the afternoon's performance of Guillaume Tell was cancelled during the second intermission after the person sprinkled the powder into the pit.

"As a safety precaution, the Met cancelled the remainder of the performance," Neuman said in a statement.

A police spokeswoman said the person who sprinkled the powder fled and was being sought.

Police initially said one person at the opera house requested medical attention. They later said no one was injured.

The Met also cancelled Saturday night's performance of L'Italiana in Algeri because of the investigation.

Audience members at Guillaume Tell described the confusion as the intermission went on longer than usual.

A Met representative at first announced that a technical issue was causing the delay, but 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, from Toronto in Canada. "As we were exiting the building, I noticed the counter-terrorism unit going into the building."