Helen Hagnes Mintiks' violin sat unused on her chair during the final ballet at the Metropolitan Opera House Wednesday night, and when the curtain rang down at 11:15 p.m. a member of the orchestra notified police.

Twelve hours after the violinist disappeared from the orchestra pit during intermission, her nude body was found in a ventilation shaft on the third floor of the opera.

Police said that Mintiks, 31, had been bound and gagged before she was dropped into the shaft, but that they were not yet sure of the cause of death.

The last time she was seen was at 9:30 p.m. in the women's locker room at the opera house. Police said she told one of her colleagues that she was going to see ballet star Valery Panov, who has been performing with the Berlin Ballet Co. at the opera house since July 15.

Mintiks, a freelance violinist, had been hired for the two-week run of the show, which leaves New York Saturday for the Kennedy Center.

Panov told reporters today that he did not know the woman and did not know that she was planning to visit him.

Panov, who emigrated from the Soviet Union six years ago, said that performers commonly see him before performances and during intermissions.

"Every day, 50 or 60 people come to see me," he said through an interpreter.

Manhattan detective Richard Nicastro said Mintiks probably had a chance encounter with her murderer, but said the assailant must have had a good knowledge of the layout of the Metropolitan Opera House, which is part of the Lincoln Center complex on Manhattan's revitalized upper West Side.

The woman was last seen alive in what is the equivalent of the basement of the opera house.

Her body had been stuffed into the ventilation shaft from the roof of the building. The only access to the roof is from the sixth floor, according to Anthony Bliss, executive director of the Metropolitan Opera Association.

Bliss said that the sixth floor -- which houses a restaurant, a kitchen and offices of the Canteen Corp. caterers -- would be virtually deserted late at night except for occasional security checks. He said the floor could be reached either by stairs or elevators but that even screams would not likely be heard.

A Manhattan detective discovered Mintiks' body resting on a beam between the third and fourth floors of the building shaft at about 8:30 this morning.

Police said she was never seen after leaving the locker room but her absence was not noticed until well after 10:30 p.m. because the orchestra did not perform in the first ballet after the intermission, "Five Tangos."

Opera house security officers began to search for her and police arrived just after midnight. Her husband, sculptor Janis Mintiks, waited for his wife outside the opera house until 12:30 a.m., then made a missing-persons call to the police when she did not appear.

The Mintiks' residence is about a half-mile from Lincoln Center at 75th and Columbus Avenue.

Police and Metropolitan Opera House security officers searched the building throughout the night.

Bliss said that security will be substantially increased for tonight's performance, but that he had never received complaints from performers that security at the opera house was inadequate.

Helen Mintiks was born in Vancouver, British Columbia, and came to New York City in 1968 to study violin at Juilliard.

A school official said she received bachelor's and master's degrees and left Juilliard in 1974.

On her application to Julliard she wrote that she has "been performing and competing since I was 4 years old." At age 11 she won a $1,000 violin in a British Columbia competition and has played in orchestras in British Columbia and Montreal.