The 84-year-old country legend was performing at the USANA Amphitheatre when he began to experience breathing problems and was taken to a local hospital, according to Billboard.

Nelson gave an update on Twitter early Monday morning, blaming the incident on altitude sickness due to the venue’s 4,300-foot altitude.

“I am sorry to have to cut the SLC show short tonight,” he wrote. “The altitude got to me. I am feeling better now & headed for lower ground.”

Christie Marcy, a music writer for Salt Lake Magazine who attended the concert, told the New York Daily News that the singer appeared to have “a hard time keeping up with the band” during the first half hour of the show.

A bandmate told the crowd that Nelson needed a break after the singer stepped off stage. However, a woman took the microphone five minutes later to tell the crowd the show was over.

“Willie loves ya’ll. He wants you to get home safe, but the show’s over,” she said, according to Marcy.

This is Willie I am sorry to have to cut the SLC show short tonight The altitude got to me I am feeling better now & headed for lower ground

— Willie Nelson (@WillieNelson) August 14, 2017

Nelson canceled several shows in late January and early February due to a “bad cold,” but he has since returned to the road.

In March, his publicist corrected reports that the singer was “deathly ill,” insisting that he was instead “perfectly fine,” according to Billboard.