Colombia was investigating on Wednesday what made a charter plane crash into its northwestern mountains, killing 71 people including most of a Brazilian football team and 20 journalists.
Football fans were in tears in the team's hometown of Chapeco and their opponents mourned in the Colombian city of Medellin, where the doomed flight crashed on Monday.
Officials and media reports in Brazil and Colombia speculated that the plane might have run out of fuel or suffered a technical fault.
The Brazilian club Chapecoense Real was on the way to crowning a fairytale year in the Copa Sudamericana final against Medellin side Atletico Nacional.
The crash cut short their dream, sending the football world into mourning.
Announcing the crash on Monday night, the aviation authority said the plane had reported electrical problems just before the crash.
But a Colombian military source told AFP: "It is very suspicious that despite the impact there was no explosion. That reinforces the theory of the lack of fuel."
Colombia's civil aviation authority said in a statement it hoped to establish the cause of Monday night's crash "as soon as possible."
British and Brazilian investigators headed to Colombia to help with the probe, authorities said.
The charter flight run by Bolivian airline LAMIA crashed in mountains at an altitude of 3,300 metres as it approached its destination, authorities said.
Officials said the weather on the night was bad.
Along with 71 bodies, investigators recovered the black boxes from the British Aerospace 146 charter plane from the remote crash site.
"When the black box is opened, nothing will be lost. It will reveal everything," said Colombian Transport Minister Jorge Eduardo Rojas.
Bolivian civil aviation chief Cesar Varela told reporters "the crew had their licences in order. Everything was in order."
Six people miraculously survived the crash. Three of the survivors were footballers, but goalkeeper Jaqson Follmann had his right leg amputated, said the San Vicente Foundation Hospital outside Medellin.
Two flight crew and a journalist following Chapecoense for the game against Medellin also survived.
Four people did not turn up for the flight, including a journalist and two politicians.
"It's one of those things in life. Only God knows why I ended up staying behind," said Luciano Buligon, the mayor of Chapeco in southern Brazil.
He arrived on Wednesday in Medellin to oversee the return of the bodies.
Brazil ordered three days of national mourning for the team.
Fans flocked to the Chapecoense stadium to mourn the team, who have emerged from nowhere over the past two years to take South American football by storm.
"The pain is terrible. Just as we had made it, I will not say to the top, but to have national prominence, a tragedy like this happens," club vice president Ivan Tozzo told Globo SporTV.
Other Brazilian clubs have offered them players so they can continue competing. Special funds have also been set up.
Football legends Pele and Maradona and current superstars Lionel Messi and Cristiano Ronaldo led tributes to the Chapecoense team.
Pope Francis said in a statement he was "deeply grieved" by the crash.
The Spanish football league said next Saturday's blockbuster clash between Barcelona and Real Madrid will be preceded by a minute's silence for the crash victims.
Atletico Nacional called for a gathering in support of the victims on Wednesday evening.
It called on fans to come dressed in white with candles to the Atanasio Girardot, where the first-leg semi-final game was meant to be played.
"Let this sadness be turned into a legacy of hope and the passion of dreams," it said on Twitter.
Rescue teams recover bodies of victims of the LAMIA airlines charter that crashed in Colombia on Tuesday.