The members of hugely successful pop group One Direction said Thursday they were "completely devastated" by the death of bandmate Liam Payne, who fell from the balcony of his Buenos Aires hotel room at the age of 31.

Family members said they were "heartbroken" as condolences poured in from the world of music, fans and the office of British Prime Minister Keir Starmer.

Singer Rita Ora interrupted a concert, saying she "can't even sing." NSYNC said the bandmates were "deeply saddened." And the Backstreet Boys, as well as Rolling Stones guitarist Ronnie Wood, were also among those who paid tribute to the British singer.

In Argentina, an autopsy suggested that Payne had not tried to stop his fall on Wednesday and "may have fallen in a state of semi or total unconsciousness" before his death.

"We're completely devastated by the news of Liam's passing and when everyone can, there will be more to say," One Direction bandmates Niall Horan, Harry Styles, Louis Tomlinson and Zayn Malik said on social media.

"But for now, we will take some time to grieve and process the loss of our brother, who we loved dearly," they said.

In a separate tribute on Instagram, Styles said Payne's "greatest joy was making other people happy."

"The years we spent together will forever remain among the most cherished years of my life. I will miss him always, my lovely friend," he wrote.

Tomlinson described Payne as "the kind brother I'd longed all my life for."

"Liam was, in my opinion, the most vital part of One Direction," he said on Instagram.

"His experience from a young age, his perfect pitch, his stage presence, his gift for writing. The list goes on. Thank you for sharing us, Liam."

Payne was found dead after hotel staff called emergency services twice to report "a guest who is overwhelmed by drugs and alcohol and destroying his room," according to leaked audio.

"I don't know if the guest's life is in danger. But he has a room with a balcony and we're a little afraid that he might do something life-threatening," an employee said.

Family remembers

Payne, the father of a seven-year-old boy, shared with Girls Aloud star Cheryl Tweedy he had spoken publicly about struggles with alcohol and coping with fame from an early age.

He had been staying in a room on the Casa Sur hotel's third floor, with a balcony overlooking a rear patio that was about 14 meters (45 feet) high.

Post-mortem results indicated that he was alone at the time of the fall and "was going through an episode of substance abuse," prosecutors said.

The singer suffered "multiple traumas" and "internal and external hemorrhaging," they said.

Payne's family issued a statement saying they would remember him for "his kind, funny and brave soul" and asking for privacy.

Mikey Graham, a member of the 1990s Irish boy band Boyzone, suggested that record companies "have psychologists on their books from now on in his memory as a duty of care for the vulnerability of their young talent."

"Fame can be very damaging, especially in today's world," he wrote on X.

Adolescence lost

The Clarin newspaper published photos Wednesday of what it said was the interior of Payne's room, with white powder on a table next to a piece of aluminum foil and a lighter, and a television with a broken screen.

The prosecutor's office said substances that appeared to be "narcotics and alcoholic beverages" had been found in the room, with pieces of furniture and other objects broken.

The results of medical and toxicological tests on Payne's body have not been made public.

One Direction began in 2010 when the then teenagers appeared on the British television contest "The X Factor."

They went on to release an album of radio-ready songs each year in time for the holiday shopping season and became one of the highest-grossing live acts in the world.

In 2016, after Malik left, the group said it was on an indefinite hiatus but not splitting up.

Payne's first solo single, "Strip That Down," peaked at number three on the U.K. charts and number 10 on the U.S. Billboard top songs list.

But in recent years, he had spoken openly about struggles with alcoholism and fame.

In a 2023 video posted to his YouTube account, he said he had spent time in rehab and discussed his efforts to stop drinking, "I kind of became somebody who I didn't really recognize anymore."

Last year, he said he was working on a second solo album and released a single this March.

Distraught fans – most in their 20s and 30s – gathered near the scene in Buenos Aires soon after news of Payne's death was announced Wednesday, many crying.

"I feel like it's a part of adolescence lost," said Lena Duek, 21.

Starmer's office offered "sincere condolences" to Payne's family and friends.

In Codsall in England, where Payne's parents live, residents voiced a mixture of shock and sadness on Thursday.

"I think everybody's talking about it because everybody knows Liam. Knows of Liam ... because he was one of us," Maria Davies, 67, told Agence France-Presse - (AFP).