In the sometimes chaotic exchange with the air traffic tower, the pilot of the British-built jet could be heard repeatedly requesting authorisation to land.

“Complete electrical failure, without fuel,” he said in the tense final seconds before the plane set off on a four-minute death spiral that ended with it slamming into a mountainside on Monday night.

A female controller could be heard giving instructions as the aircraft lost speed and altitude about eight miles from Medellin’s international airport.

Just before going silent the pilot said he was flying at an altitude of 9,000 feet and made a final plea for a landing code: “Vectors, senorita. Landing vectors.”

The recording, obtained on Wednesday by Colombian media, appeared to confirm the accounts of a surviving flight attendant and a pilot flying nearby who overheard the frantic exchange.

These, along with the lack of an explosion upon impact, point to a rare case of fuel running out as a cause of the crash of the jetliner, which was flying at its maximum range.

For now, authorities are avoiding singling out any one cause of the crash, which killed all but six of the 77 people on board, including members of Brazil’s Chapecoense soccer team travelling to Medellin for the Copa Sudamericana finals – the culmination a fairy tale season that had electrified soccer-crazed Brazil.

A full investigation is expected to take months and will review everything from the 17-year-old aircraft’s flight and maintenance history to the voice and instruments data in the black boxes recovered on Tuesday at the crash site on a muddy hillside.

The US National Transportation Safety Board was taking part in the investigation because the plane’s engines were made by an American manufacturer.

As the probe continued, mourning soccer fans in Medellin and the southern Brazilian town of Chapeco, where the team is from, were converging on the two cities’ soccer stadiums for simultaneous candlelight vigils.

The six survivors were recovering in hospitals, with three in critical but stable condition, while forensic specialists worked to identify the victims so they could be transferred to a waiting cargo plane sent by the Brazilian air force to repatriate the bodies.

One key piece to unlocking the mystery could come from Ximena Sanchez, a Bolivian flight attendant who survived the crash and told rescuers the plane had run out of fuel moments before the crash.

Investigators were expected to interview her on Wednesday at the clinic near Medellin where she is recovering.

“‘We ran out of fuel. The airplane turned off,”‘ rescuer Arquimedes Mejia quoted Sanchez as saying as he pulled her from the wreckage. “That was the only thing she told me,” he told The Associated Press.

In a four-minute recording circulated on social media, Upegui described how he heard the flight’s pilot request priority to land because he was out of fuel.

Growing ever more desperate, the pilot eventually declared a “total electrical failure,” Upegui said, before the plane quickly began to lose speed and altitude.

“I remember I was pulling really hard for them, saying ‘Make it, make it, make it, make it,”‘ Upeqgui says in the recording. “Then it stopped. … The controller’s voice starts to break up and she sounds really sad. We’re in the plane and start to cry.”

No traces of fuel have been found at the crash site and the plane did not explode on impact, one of the reasons there were six survivors.

– AAP