Sam Smith was scheduled to perform Friday night at the iHeartRadio Music Festival in Las Vegas until he cancelled at the last minute due to what was described as a “vocal emergency.”

On Saturday, the singer gave an update, telling fans on Twitter that he’d been checked by a doctor, and why he is “ok,” he will need to rest his vocal chords for a week before heading out on his Asian tour.

The music festival’s emcee Ryan Seacrest broke the news of the cancellation to fans from onstage at the festival, reports Variety.

“Due to unforeseen circumstances which transpired after his rehearsal, it became clear that Sam Smith would unfortunately not be able to perform tonight,” Seacrest told the crowd. “We love Sam. Sam has been part of our iHeart family for many, many years and we look forward to seeing him really soon.”

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Shortly after Seacrest’s announcement, a rep for the “Lay Me Down” singer issued a statement confirming Seacrest’s onstage announcement: “Sam is extremely sorry he is unable to perform at tonight’s show and wants to apologize to his fans.”

Smith later tweeted that “unforeseen circumstances which transpired after rehearsal” had left him “unable to perform,” and he offered an apology to disappointed fans who had come out to seem him perform.

While there was initially no official word as to what those “unforeseen circumstances” might be, Variety reports that “multiples sources” claim that “Smith inexplicably lost his voice.”

According to Variety, Smith had been complaining of pain in his throat; because his performance would have been broadcast live throughout the iHeartRadio network, a decision came down to cancel at the 11th hour, with Childish Gambino (a.k.a. Donald Glover) starting his set earlier than scheduled.

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Variety also reported that shortly after the cancellation, at approximately 10 p.m. Friday night, Smith exited the venue and boarded a chartered flight to Boston. Why Boston? One guess, noted Variety, was that Smith may be paying a visit to Massachusetts General Hospital’s Dr. Steven Zeiltels, described as “an expert in the field of vocal cord and node damage” who has successfully performed vocal cord surgery on such singers as Adele, Aerosmith frontman Steven Tyler and “Sound of Music” star Julie Andrews.