Placido Domingo’s performance in Madrid has been cut following an internal investigation by the American Guild of Musical Artists over sexual harassment allegations.

Last summer, allegations against the opera star surfaced; Domingo was accused of pressuring women into engaging in sexual relationships with him by dangling jobs and sometimes punishing women professionally when they refused his advances. After the news of allegations broke, various American arts organizations – including the San Francisco Opera and the Philadelphia Orchestra – cancelled his appearances. Organizations across Europe, however, opted to wait until investigations were complete.

On Tuesday, the union representing American opera performers, the American Guild of Musical Artists, released the results of their internal investigation and found that Domingo “engaged in inappropriate activity, ranging from flirtation to sexual advances, in and outside of the workplace.”

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Domingo, 78, issued a public apology on Tuesday, noting that he has “taken time over the last several months to reflect on the allegations that various colleagues of mine have made against me.”

“I am truly sorry for the hurt that I caused them,” he said. “I accept full responsibility for my actions, and I have grown from this experience. I understand now that some women may have feared expressing themselves honestly because of a concern that their careers would be adversely affected if they did so. While that was never my intention, no one should ever be made to feel that way.

“I am committed to affecting positive change in the opera industry so that no one else has to have that same experience. It is my fervent wish that the result will be a safer place to work for all in the opera industry, and I hope that my example moving forward will encourage others to follow.”

Following the results of the investigation, Spain’s National Institute of Performing Arts and Music cancelled Domingo’s upcoming performance. The institute said it came to the decision “in solidarity with women affected and realizing that responsibility recognized by the artist.” He was originally slated to perform at the Teatro de la Zarzuela in Madrid on May 14 and 15 to celebrate the 50th anniversary of his debut in the city.

“We are very disappointed to learn of Zarzuela’s decision to cancel the scheduled performance, but understand and respect it,” Nancy Seltzer, a spokeswoman for Domingo, said in a statement to the New York Times. “Placido Domingo hopes that he gets the opportunity to sing there again.”

While Domingo is still slated to perform throughout Europe this summer – with performances at the Hamburg State Opera, Madrid’s Teatro Real, and London’s Opera House – organizers of the Salzburg Festival in Austria said they are still unsure if he will perform until they seek further information on the matter.

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Earlier this week, the American Guild of Musical Artists union, which had conducted the investigation, reportedly tried to negotiate a $500,000 payment from Domingo which it said would cover the costs of its investigation and pay for anti-harassment efforts. However, the Times reported that the deal fell apart after details of the investigation, which the union had promised to keep secret, were leaked on Tuesday. In a statement, the union said that it was “never planning to publicly release the specific details of its internal investigation” and “any suggestion that the union was being paid to withhold information is patently false.”

At this time, the Los Angeles Opera, which Domingo originally helped found – and then stepped down from last year – is still conducting its own investigation. A spokesperson for the opera told CNN that they “expect to complete that process shortly.”