Céline Dion had to delay her Las Vegas show due to “unforeseen medical symptoms” that involve muscle spasms, according to Health.

The 53-year-old singer said she was “heartbroken” to have to push back the November 5 opening date of her new show at The Theatre at Resorts World.

Dion canceled 21 headlining performances from November 5 to 10 and from January 19 to February 5, She has been experiencing “severe and persistent muscle spasms,” preventing her from performing, according to a press release.

The My Heart Will Go On singer is being evaluated and treated by her medical team, but her muscle spasms are keeping her from taking part in the show’s ongoing rehearsals.

She said in a statement, “I’m heartbroken by this. My team and I have been working on our new show for the past eight months, and to not be able to open this November saddens me beyond words. My partners at Resorts World Las Vegas and AEG have been working around the clock to get this brand-new state-of-the-art theatre ready, and it’s absolutely beautiful.”

“I feel so bad that I’m letting them down, and I’m especially sorry for disappointing all the fans who’ve been making their plans to come to Las Vegas,” Dion continued. “Now, I have to focus on getting better… I want to get through this as soon as I can.”

John Meglen, President of Concerts West/AEG Presents, said the new show dates would be announced “whenever Céline is ready.”

He said, “Céline is family to us, and the most important thing now is for her to focus on feeling better. In our two-decade long relationship with Céline, we’ve certainly learned how dedicated and resilient she is, and that she is most happy when she’s on stage doing what she loves most, performing for her fans.”

Dion’s opening night show on November 5 was slated to be a special performance to benefit COVID-19 relief.

However, she will continue her Courage World Tour as planned, with a kick-off date scheduled for March 9, 2022. The story originally appeared on PEOPLE and Health.