'I can't even tell you how devastated I am by this," Taylor Swift wrote on Instagram.

The cause of death for Ana Clara Benevides Machado has not yet been announced. The office of Rio’s public prosecutor opened a criminal investigation and said Benevides body was being examined. But concert-goers complained they were not allowed to take water into Nilton Santos Olympic Stadium despite soaring temperatures, and federal authorities announced that free water would be made available at all future concerts.

In a handwritten note shared on her social media, Swift said she had a "shattered heart." "There’s very little information I have other than the fact that she was so incredibly beautiful and far too young,” the singer wrote of the young woman.

The show's organiser, Time4Fun, said on Instagram that paramedics attended to Benevides after she reported feeling unwell. She was taken to a first-aid center and then to a hospital, where she died an hour later, the statement from the Brazilian live entertainment company said.

Fans who attended the Friday show said they were not allowed to bring water bottles into the stadium even though Rio and most of Brazil have had record-breaking temperatures this week amid a dangerous and lasting heat wave. The daytime high in Rio on Friday was 39.1˚C, but it felt much hotter.

Apparent temperature — a combination of temperature and humidity — hit 59˚C on Friday morning in Rio, the highest index ever recorded there.

Elizabeth Morin, 26, who recently moved to Rio from Los Angeles, described "sauna-like” conditions inside the stadium. "It was extremely hot. My hair got so wet from sweat as soon as I came in,” she said. "There was a point at which I had to check my breathing to make sure I wasn’t going to pass out.”

Morin said she drank plenty of water but saw "a good amount of people looking distressed” and others "yelling for water.” She said she was able to get water from the sidelines of the area she was standing in, but that water was a lot harder to access from other parts of the stadium, "especially if you were concerned about losing your specific position.”

During the show, Swift paused her performance and asked from the stage for water to be brought to a group of people who had successfully caught the singer's attention, according to Morin.

"They were holding up their phones saying ‘We need water,’” she recalled.

Justice Minister Flávio Dino said on X that the ministry would implement "emergency rules" in response to the situation. He later announced that "water bottles for personal use, in suitable material, will be allowed" at concerts and other events and that show producers must provide free and easily accessible drinking water.

Swift has two more shows scheduled in Rio, one on Saturday and one on Sunday. State prosecutors said in a statement they would "monitor measures that seek to avoid new problems and guarantee the protection of the health of the public.”

Before the show, Benevides posted a video of herself on Instgram wearing a Taylor Swift T-shirt and waiting in line to enter the stadium while seeking shade under an umbrella. Like her, thousands of fans waited hours in the sun before being allowed inside.

She told her followers while fanning her face that she’d arrived at 11am — the show began around 7:30pm — and was "still in the mess.”

Benevides' friend, Daniele Menin, who attended the concert with her, told online news site G1 that her friend passed out at the beginning of the concert, as Swift performed her second song, "Cruel Summer.”

"We always said that when (Taylor Swift) came to Brazil we would find a way to go. The ticket was very expensive, but we still found a way”, Menin told G1.

Rio de Janeiro Mayor Eduardo Paes said on X the "loss of a young woman’s life ... is unacceptable.”

While authorities are investigating the circumstances of the death, Paes wrote, the municipality will demand Saturday that the show’s production company provide new water distribution points, more brigades and ambulances, and advance entrance to the show by one hour.

"I'm not going to be able to speak about this from stage because I feel overwhelmed by grief when I even try to talk about it,” she wrote. "I want to say now I feel this loss deeply and my broken heart goes out to her family and friends.”

Associated Press