Ten people have been killed and at least three injured in a fire at the training centre of the Rio de Janeiro football club Flamengo.

Firefighters were called to the blaze at the Ninho de Urubu training ground just after 5am on Friday, a fire official told the Associated Press.

“Those who died were athletes,” said Beatriz Busch, the public health secretary for the state of Rio de Janeiro, adding that their identities had not been released and the cause of the fire was unknown. Busch said two of the injured people were in a stable condition while the other was critically ill.

Firefighters said that while some people had managed to escape the flames, the ferocity of the blaze prevented rescuers from entering the facility. “We managed to rescue the victims that were outside,” said a fire service spokesman, Lt Col Douglas Henaut. “The place was completely overtaken by fire. As much as we tried to get inside and find people still alive that wasn’t [possible] … We found only bodies inside.”

“We can’t tell you the cause of the fire; that needs to be investigated,” he added.

One young player said the fire had started in his room. “The air conditioner caught fire, and I ran out,” said Felipe Cardoso, a midfielder with the under-17 side. “Thank God I managed to run and I’m still alive.”

Aerial footage showed twisted corrugated iron roofs and piles of charred items. Nearby trees were also scorched. The fire followed days of heavy rain that killed at least six people in the city.

An AP reporter outside the complex saw two ambulances and a fire engine enter. The facility was closed, and no officials emerged to address media. Family members, friends and neighbours gathered outside in the hope of getting information.

Jefferson Rodrigues, who runs a small inn near the club, said he had been in contact with a 15-year-old player. “I am very happy. I just spoke to Caix Suarez and he is alive,” he said. “He lost his phone and all of his things, but the important thing is he is alive.”

João Pedro da Cruz, a 16-year-old player in the Flamengo youth league, told the news portal G1 that he had decided not to stay the night at the facility and had gone to a friend’s house instead. “The majority of [the team] stayed, my friends stayed,” he said. “Today I woke up and heard this terrible news.”

As news of the fire broke, several other players and teams expressed their condolences on Twitter.

Vinicius Junior, the teenage Real Madrid forward who trained there before joining the Spanish club last year, tweeted: “What sad news! Praying for everyone! Strength, strength and strength.

“We are extremely sad and shaken by the news of the fire,” tweeted Chapecoense, a team in southern Brazil that lost 22 players in a plane crash in 2016.

Flamengo made no official statement other than to tweet that the club was in mourning, but rival teams across Brazil, including fellow Rio sides Botafogo, Fluminense and Vasco da Gama, expressed their solidarity.

The tragedy came a day before the side were due to play Fluminense, their arch-rivals, at the Maracana stadium. The derby match is expected to be postponed.

Flamengo, the alma mater of Brazilian national team players including Zico, Junior and Leonardo, is one of the best-supported clubs in the country and is famous around the world.

Known by fans as the Red-and-Black, they won the Copa Libertadores, South America’s version of the Champions League, in 1981 and lifted the Intercontinental Cup a few months later.

Zico, who is outside Brazil, wrote on Instagram: “What a shock getting this news here on the other side of the world. May the Red-and-Black nation have strength and faith to get through this moment.”

One of Flamengo’s highest-profile fans, the country’s vice-president, Gen Hamilton Mourão, also expressed his condolences. “As a fan and sportsman I stand in solidarity with the families, the club and the Red-and-Black nation,” he tweeted. “May God comfort all.”

Like many professional clubs in Brazil, Flamengo have a youth development programme for promising young players in their early teens. Many, particularly those who live outside Rio, stay at the facilities while training.

After years of financial difficulties, Flamengo expanded its facilities last year. In addition to accommodation for young players, they include several pitches, an aquatic park, a gym, a medical centre and a mini-stadium.

This report includes material from the Associated Press and Reuters