Former Sale second row Hyron Andrews has died at his Johannesburg Lions' team hotel before their Champions Cup match at La Rochelle on Saturday.
A statement from SA Rugby stated that his death had been an "accident" and that the 31-year-old had "died after a fall".
"We are heartbroken by the passing of Hyron," said Lions chief executive Rudolf Straeuli.
"He was not only a gifted rugby player, but also a cherished member of our Lions family having recently joined us this season.
"On behalf of our chairman, Mr Altmann Allers, the board and everyone at the Lions, I extend our deepest sympathies to [Andrews' wife] Maighlin, their young sons Hendrix and Emerson and the entire Andrews family.
"We stand with them in their sorrow and will remember Hyron with great affection and respect."
The Lions will fulfil their fixture against La Rochelle, which kicks off at 17:30 BST, in Andrews' honour, while a moment's silence will be observed at all the opening round's fixtures.
"This is terrible and distressing news; our hearts go out to Hyron's family and the whole Lions rugby community," said Mark Alexander, president of the South African Rugby Union.
"There are no words to adequately convey our shock and the depth of sympathy we feel for his wife Maighlin, and for his extended family, friends, team-mates and loved ones during this time of immense sorrow.
"His untimely passing is a devastating loss, and we share in the grief of all who knew and loved him."
Andrews left Sale in the summer to return to his native South Africa. He made 45 appearances for the club after arriving in February 2024 from the Durban-based Sharks as injury cover for England international lock Jonny Hill.
"Hyron was just a brilliant guy and a brilliant team-mate," said Sale director of rugby Alex Sanderson.
"He was so skilled on the field but off it, he was always someone you would want to have a beer with.
"He was funny and charismatic in his own unique, dry way and the lads, to a man, loved playing with him and being around him.
"It was a big move for Hyron and Maighlin to come to England, but he truly made a second home in Manchester. It was incredible to see how he and his family embraced the club and area.
"Most importantly, he was a loving husband to Maighlin and a doting father to his two gorgeous boys. It was an absolute privilege to get to know him and it's just absolutely devastating for everyone."
While he was yet to earn senior international honours, Andrews had represented the Junior Springboks in 2015.
Andrews' death comes 10 years on from the sudden death of Munster coach Anthony Foley in Paris before a Champions Cup fixture.
Foley, 42, died in his sleep on the eve of a match against Racing 92 after a heart condition caused fluid to build up in his lungs.
Munster's present-day players will wear commemorative tops, featuring the Munster club crest and Foley's shirt number eight as part of their pre-match routine at their match against Racing on Saturday.
The Lions, who play their home matches at Ellis Park, are making their first appearance in Europe's premier club competition, with South African sides introduced into the continental competition in the 2022-23 season.
They have won two of their first three matches in the United Rugby Championship so far this season, including beating defending champions Leinster in their first game of their campaign.