Taylor Swift said she was "devastated" by the death of a fan before her Brazil show on Friday.
The performer is on the South American leg of her sold-out tour, after a mammoth run in the US.
Writing on Instagram, Swift said: "I can't believe I'm writing these words but it is with shattered heart that I say we lost a fan earlier tonight before my show.
"I can't even tell you how devastated I am by this.
"There's very little information I have, other than the fact that she was so incredibly beautiful and far too young."
Swift added she would not be addressing the incident on stage in Rio de Janeiro because she was "overwhelmed by grief".
She concluded: "I want to say now I feel this loss deeply and my broken heart goes out to her family and friends. This is the last thing I ever thought would happen when we decided to bring this tour to Brazil."
There is no official information surrounding the fan's death.
Local media reported temperatures in the Brazilian stadium reached up to 60C at one point, adding Swift paused her show and asked for water to be distributed among concertgoers during the set.
In one video, she is seen saying: "There's people that need water right here, maybe 30, 35, 40 feet back.
"So whoever is in charge of giving them that, just make sure that happens. Can I get a signal that you know where they are?"
Swift is scheduled to perform in Rio again on Saturday and Sunday evening, before moving to Sao Paolo next weekend.
Earlier this week, the Shake It Off singer added two more dates to her London leg at Wembley next August, which sold out almost immediately.