The move , which was reported first by The Los Angeles Times, caused ripples in that city, where the museum was widely seen as an ambitious project .

Union officials , who filed a petition with the National Labor Relations Board on Friday seeking to represent about 70 employees, called the dismissals “clearly retaliatory.” An employee who lost his job said that the decision was reminiscent of how Guess had reacted to unionization efforts 20 years ago.

The organizing at the Foundation was the latest in a series of recent such efforts at museums across the country including the New Museum and the Guggenheim in New York, and the Frye Art Museum in Seattle.

The creators, Maurice and Paul Marciano, started Guess in 1981 with two other brothers, then became known as art collectors. Maurice served for several years on the board of the Museum of Contemporary Art in Los Angeles. He is now chair emeritus. In 2017, the two opened their private institution in a former Masonic Temple on Wilshire Boulevard that their foundation bought for $8 million. The collection includes about 1,500 works by artists including Cindy Sherman, David Hammons and Damien Hirst, and the museum has put on shows by Jim Shaw and Ai Weiwei.

On Wednesday, the museum’s website said: “ The foundation will remain closed to the public until further notice .” Two shows, by the artists Donna Huanca and Anna Uddenberg, that had initially been scheduled to run until Dec. 1 were listed as having ended on Monday.