Taylor Swift has postponed a concert she was due to perform in Rio de Janeiro on Saturday, after a fan died while attending her show on Friday.
The decision came as thousands of people were already at the stadium as part of her record-breaking Eras tour.
Posting on Instagram, Swift said: "The safety and well-being of my fans, fellow performers and crew has to and always will come first."
Brazil is experiencing an unprecedented heatwave, triggering health alerts.
Authorities warned of the danger to life as it recorded a heat index, which combines temperature with humidity, of 59.3C (138.7F) on Friday followed by 59.7C (139.5) on Saturday.
The US pop star's show on Monday will still go ahead.
In a statement on Instagram, the pop star said she was "devastated" over the death of a fan and that her heart was "shattered", adding: "She was so incredibly beautiful and far too young."
"I can't believe I'm writing these words but it is with a shattered heart that I say we lost a fan earlier tonight before my show," Swift wrote.
"I can't even tell you how devastated I am by this."
According to the organisers, 23-year-old Ana Clara Benevides Machado had sought help at the stadium after feeling unwell. She was transferred to hospital but died one hour later.
According to Brazilian newspaper Folha de Sao Paulo, the cause of death was given as cardiorespiratory arrest.
Taylor Swift, 33, said she would not be able to speak about the incident from the stage because she felt "overwhelmed by grief" whenever she tried to talk about it.
"I want to say now I feel this loss deeply and my broken heart goes out to her family and friends."
She added that this was "the last thing" she thought would happen when she brought the tour to Brazil.
Swift said she had little other information about the death.
In videos and pictures circulated on social media, Swift was later seen urging staff at the stadium to give water to fans during the concert.
At one point, while singing All Too Well, she was seen throwing a water bottle into the crowd.
Rio Mayor Eduardo Paes posted on X (formerly known as Twitter) that what happened was unacceptable and he had asked the show's producers for several changes including extra water distribution points and more emergency services on standby.
Brazil's Justice Minister Flávio Dino also posted on X that fans must be allowed to bring in water bottles to the venues.
He ordered the company organising the Eras Tour in Brazil, T4F Entertainment, to provide fans with free and easily accessible drinking water.
The minister's statement came after concert-goers were banned from bringing in their own water bottles.
Swift arrived in Brazil earlier this week for her record-breaking tour, with Rio de Janeiro's Christ the Redeemer statue illuminated to welcome her to the country.
The pop star is due to play two more shows in Rio before heading to Sao Paulo.
Swift had to cancel previously scheduled performances in the country because of the Covid-19 pandemic.
She is coming to the UK in June 2024, where she will play Edinburgh, London, Liverpool and Cardiff.
The BBC has approached T4F Entertainment, for a response.
Additional reporting by Katy Watson in Sao Paulo and Emily McGarvey in London