Ten people have died and at least three others have been injured after a fire broke out at the youth training ground of Brazilian football club Flamengo on Friday, according to state-run news agency Agencia Brazil.
The blaze engulfed a dormitory at the youth team center where the players were sleeping.
Flamengo are one of Brazil's biggest and most popular clubs, playing their home matches in Rio de Janeiro.
The Governor of Rio, Wilson Witzel, has announced three days of mourning to remember the victims of the tragedy, Agencia Brazil reported.
The derby between Flamengo and bitter Rio rivals Fluminense -- one of the biggest matches on the Brazilian calendar -- had been due to take place on Saturday 9 at the Maracana but has been postponed.
Three of the 10 victims have been named by Agencia Brazil as youth-team players 15-year-old Jonathan Cruz Ventura, 14-year-old Cauan Emanuel Gomes Nunes and 15-year-old Francsico Diogo Bento Alves.
General Hamilton Mourao, Brazil's Vice-President and one of the club's most high-profile fans, wrote: "As a fan and sportsman I stand in solidarity with the families, the club and the Red-and-Black nation. May God comfort all."
Real Madrid forward Vinicius Junior, who joined the club from Flamengo last year, said: "Just remembering the nights and days I spent at the training center, it gives me goosebumps.
"I still can't believe it but praying for all. God bless everyone's family."
Flamengo posted that the club "is in mourning."
Pele, Brazil's three-time World Cup winner, tweeted: "My day began with the news about the fire at Flamengo's training ground -- a place where young people pursue their dreams.
"It's a very sad day for Brazilian football."