Colombian authorities say evidence is growing that a plane carrying a Brazilian football team crashed because it ran out of fuel as it tried to land.
Civil aviation chief Alfredo Bocanegra said an initial inspection at the site indicated the plane “did not have fuel at the moment of impact”.
It appeared to corroborate a leaked tape in which the pilot can be heard requesting permission to land due to an electric failure and lack of fuel.
Only six of 77 people aboard survived.
“Upon arriving at the scene of the accident, and having been able to do an inspection of all of the remains and parts of the plane, we can affirm, clearly, that the aircraft did not have fuel at the moment of impact,” Mr Bocanegra told a news conference.
“Therefore, we have begun a process to investigate to clear up for what reason this aircraft had no fuel at the time of impact.”
Speaking at the same news conference, civil aviation official Freddy Bonilla said regulations stipulated that aircraft must have 30 minutes of extra fuel in reserve so as to be able to reach an alternative airport in an emergency.
“In this case the plane did not have the fuel to get to an alternative airport,” he said.
He added: “The engines are the electrical source… but without fuel, obviously the electrical source would have been completely lost.”
In the leaked tape, the pilot can be heard warning of a “total electric failure” and “lack of fuel”.
Just before the tape ends, he says he is flying at an altitude of 9,000ft (2,745m).
The plane plunged into a mountainside near the Colombian city of Medellin late on Monday.
There was no explosion, which experts say could also indicate a lack of fuel.
Officials say the plane’s “black boxes”, which record flight details, will be sent to the UK to be opened by the manufacturers, the British company, BAE.
A full investigation into the crash is expected to take months.