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London's Old Vic theater said Thursday it has received 20 allegations of "inappropriate behavior" against actor Kevin Spacey during his time there.

The new complaints surfaced in an investigation triggered by a claim that the Oscar-winning star had preyed on young actors in the theater's bar, and followed last month's allegation that he made a sexual advance to a teenager in 1986.

Spacey, 58, began performing at the theater in the 1990s and served as its artistic director from 2004-15.

“There are allegations of a range of inappropriate behaviour,” the theater said in a news release, adding that none of the complainants was a minor at the time.

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“It has also not been possible to verify any of these allegations, and it is important to note that Kevin Spacey has not commented on them."

Nevertheless, it apologized that complainants had previously felt unable to come forward with concerns and that Spacey operated without "sufficient accountability” at the venue because of a "cult of personality" around him.

“The investigation found that his stardom and status at The Old Vic may have prevented people, and in particular junior staff or young actors, from feeling that they could speak up or raise a hand for help,” it said. “The Old Vic truly apologises for not creating an environment or culture where people felt able to speak freely."

Related: Here’s a growing list of men accused of sexual misconduct

Details of the allegations were not given; except for one claim, none was raised formally or informally with management at the time.

Spacey issued an apology for the Oct. 30 allegation by Anthony Rapp dating to 1986 but has not spoken in public about subsequent claims of misconduct. In his apology, Spacey wrote, "I want to deal with this honestly and openly and that starts with examining my own behavior."

In a Nov. 2 statement, his publicist said: "Kevin Spacey is taking the time necessary to seek evaluation and treatment. No other information is available at this time.”

Spacey is one of the biggest names to lose work and standing in Hollywood since The New York Times and The New Yorker detailed sexual harassment and abuse allegations against film mogul Harvey Weinstein. The reports saw allegations surface across the industry.

Spacey has also been fired from "House of Cards" and dropped by his talent agency and publicist.