The Jewish Defense League (JDL) denied today disrupting a performance of the Moiseyev Ballet by setting off a tear-gas canister inside the Metropolitan Opera House but warned that further such incidents could take place.

About 30 people had to be treated for smoke inhalation and eye irritation after the tear gas sent thousands of people running from the elegant opera house in New York's Lincoln Center last night.

A caller identifying himself as Chaim Ben-Yosef, national chairman of the JDL, last night told news agencies the JDL was responsible for the attack.

But today, Ben-Yosef denied making the calls and denied the JDL was involved, saying he thought the canister was set off by Soviet Jewish e'migre's outraged at their treatment in the Soviet Union.

Ben-Yosef also warned against attending future performances by the popular Russian folk ballet troupe because he said he expected there would be similar protests.

The Moiseyev dancers are scheduled to perform at the Kennedy Center Sept. 23-28 during the troupe's planned 15-city U.S. tour.

Police said they had made no arrests and were investigating.

The JDL is a militant Jewish organization that offers karate and gun training to Jews for "self-protection." In the past JDL members have been arrested for disrupting performances by Soviet entertainers.

Almost 4,000 people were evacuated from the opera house after the tear-gas canister was set off. The performance, the first by the Moiseyev in the United States since 1974, was canceled.

Among those fleeing the gas were Yuri Dubinin, the Soviet ambassador to the United States, and Igor Moiseyev, the 81-year-old founder and director of the company. Moiseyev said through a translator, "I don't think that anything like this could happen in the Soviet Union. But at the same time this is not the fault of the American public."

Mayor Edward I. Koch, who went to Lincoln Center, told reporters he apologized to Moiseyev on behalf of the city. Koch said Moiseyev took the incident in stride and told him, "It's probably good for business."

Police spokesman Sgt. Raymond O'Donnell said the performances would resume tonight, "but internal security will be built up.