With all but eight Broadway theaters dark, off-Broadway shows could notice a surge of interest in the busy weeks ahead, industry experts say.

On Saturday morning, the stagehands union, Local One, went on strike following months of tense labor negotiations with the League of American Theaters and Producers. Both parties have expressed interest in returning to the negotiating table, but refused to speculate on when that could happen, and would not comment on how long the work stoppage could last.

Sales of discounted ticket at the TKTS booths in Times Square and at the South Street Seaport were up over the weekend, with many off-Broadway shows selling out, a spokesman for the Theater Development Fund, which runs the booths, said.

Also, traffic doubled at Off-Broadway.com, a Web site with information about off-Broadway theaters and shows, the Web site manager, David Risley, said.

“As tragic as the situation is for Broadway, there is a silver lining for the off-Broadway world,” Mr. Risley said.

The work stoppage could also present theatergoers with the opportunity to see a show they wouldn’t have otherwise considered, an off-Broadway producer, Ken Davenport said. Tickets to his three shows, “Altar Boyz,” “Awesome 80s Prom,” and “My First Time,” sold out this weekend considerably faster than usual, he said.

“We do not necessarily play to the same people, but I think this is an opportunity to explore and try new things, especially tourists that come to New York and will not have Broadway as an option for the time being,” the president of the League of Off-Broadway Theaters and Producers, George Forbes, said.

Tickets were unexpectedly sold out for the musical “Crossing Brooklyn,” the artistic director of the company putting on the show, Jack Cummings III, said. Many of the patrons were people who work in the industry and who now, because of the strike, had the night off, Mr. Cummings speculated.

“It’s really only going to affect the theaters within walking distance of Times Square,” he said. “To me, the shows that will see the increase are the off-Broadway shows that have a more commercial bent, and maybe we will get some light spill-over.”

The stagehands are quietly walking in picket lines in front of the 31 theaters that are dark, and are handing out flyers to theatergoers that explain their side of the story.

The league has offered to refund all tickets, and posted flyers in theaters outlining the process.

In the union’s first public announcement about the strike, President James Claffey Jr. said members are “being attacked” by the league, and said the union would not go back to the negotiating table if what he considered a lack of respect was not addressed.

“I’m very proud of what our membership has chosen to do,” Mr. Claffey said. “I can’t apologize for a union fighting for its right to protect its jobs,” he added, noting that the stagehands had been working since October under league-imposed work rules.

The executive director of the league, Charlotte St. Martin, said the union left the negotiating table and “abruptly” began picketing.

“Our members are united in their commitment to achieving a fair contract,” Ms. St. Martin said at a news conference on Saturday. “The place to resolve these issues is at the bargaining table, not the picket line.”

She added yesterday: “The union wants you to believe they are the victims, the little guys.”

Mayor Bloomberg again offered city assistance to mediate the strike, and while the producers have said they will consider the offer, Mr. Claffey said he “respectfully declines” it.