A possible electrical failure is being blamed for the air disaster that killed 71 people in the mountains of Colombia, wiping out a top Brazilian soccer team.
The chartered plane was carrying players and staff from the Chapecoense club, who were on their way to Medellin for the two-game Copa Sudamericana final - which is South America's second-biggest club cup. There were also 22 sports journalists on board, to cover the end of what had been a fairytale season, and nine crew members.
Only five people survived, making it the world's deadliest air disaster this year.
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Two black boxes have been recovered from the crash site. Authorities posted pictures on Twitter this morning, saying they appear to be "in perfect condition".
Crash investigator Alfredo Bocanegra said that communication with Bolivian aviation officials suggested the plane was experiencing electrical problems.
Authorities are also investigating the possibility of engine failure, following a reported testimony from a female flight attendant that the plane ran out of fuel.
However, reports in England's Mirror newspaper claims the pilot dumped fuel in the lead-up to impact to prevent a huge explosion.
News of the possible cause comes amid reports the team was forced change flights at the last minute due to red tape.
London's The Sun reports the team could have flown directly to Medellin on their original plane, but were forced to stop in Bolivia and change onto the potentially faulty aircraft due to rules governing international flight services in South America.
A recorded phone call shows the pilot pleading with the mayor of Chapeco - the team's hometown - to try and get permission to fly direct using a Bolivian plane.
However, his request was refused because a ruling official from Brazil's National Civil Aviation Agency said the team must fly with a Brazilian or Colombian airline.
Flight LMI2933 crashed and split into two at 10:15pm local time on Monday.
Treacherous weather conditions severely hampered the rescue operation as ambulances struggled to reach the remote crash site.
Survivors were carried half an hour down a mountain on stretchers, before being taken to hospital by ambulance.
The first survivor to arrive at hospital was 27-year-old fullback Alan Rushchel, who is currently in intensive care with a spinal fracture.
Reserve goalkeeper Jakson Follmann is in hospital, and has reportedly had one his legs amputated this morning and is in a critical condition.
Female flight attendant Ximena Suarez, journalist Rafael Henzel and technician Erwin Tumiri have also been named as survivors.
Goalkeeper Marcos Danilo lived through the impact, but died in hospital after making a heartbreaking call to his wife.
It's not the first air tragedy to devastate a sporting club.
In February 1958, a British European Airways plane crashed in Germany, killing 23 people -including eight Manchester United players.
They were on their way home from Serbia after qualifying for the semi-finals of the European Cup, and had stopped in Munich to refuel.
A snowstorm forced the pilot to abort two takeoff attempts, and on the third attempt there was too much ice on the wings for the aircraft to get enough lift.
It smashed through a fence and ran into an empty house.
There were no survivors among the 75 people on board a Southern Airways DC-9 when it hit trees in the mountains of West Virginia in 1970.
The crash was the worst disaster in American sports history, with 38 members of the Marshall University Thundering Herd gridiron team killed in the explosion.
In 1972, Uruguayan Air Force Flight 571 crashed in Chile's Andes mountains with 45 people on board, including a rugby union team.
The 16 survivors lived for two months in the mountains - feeding on the remains of their fellow passengers, whose bodies had been preserved in the snow.
In December 1987, a navy plane carrying a Peruvian soccer team plunged into the Pacific Ocean, killing 16 players and the club's coach.
Eighteen players and five team officials were killed in the African country of Gabon in 1993, when a plane carrying Zambia's national soccer team crashed on the way to a World Cup qualifying game in Senegal.
The most recent air disaster with sporting links was in 2011, when a Russian plane chartered by one of the country's elite ice-hockey teams crashed during takeoff.
All but two of the 45 people on board were killed, including 27 players, two coaches and seven club officials.
Brazilian President Michel Temer has declared three days of official mourning.
Crowds have gathered in Chapeco, the club's home town, as heartbroken fans struggle to come to terms with the enormous loss.
The Cinderella team joined Brazil's first division in 2014 for the first time since the 1970s. It made it to the Copa Sudamericana finals after defeating two of Argentina's most fierce teams.
"This is unbelievable, I am walking on the grass of the stadium and I feel like I am floating," Chapecoense spokesman Andrei Copetti told The Associated Press.
"No one understands how a story that was so amazing could suffer such a devastating reversal. For many people here reality has still not struck."
FIFA President Gianni Infantino said it is a "very, very sad day for football".
"We are so sorry to hear about the aeroplane crash in Colombia, it is shocking and tragic news. At this difficult time our thoughts are with the victims, their families and friends," he wrote in a statement.
- additional reporting AP