Emiliano Sala and pilot David Ibbotson were exposed a “potentially fatal” amount of carbon monoxide before the tragic plane crash on January 21.
Sala lost his life, while Mr Ibbotson’s body has never been found, after their Piper Malibu PA-46 aircraft went down while travelling between Nantes and Cardiff earlier this year.
The Air Accident Investigation Branch have said that Cardiff City forward Sala, who had only just signed for the club, had a carbon monoxide level of 58 per cent in his blood.
That amount can cause seizures, unconsciousness or heart attacks. Anything over 50 per cent is considered potentially fatal.
It is suspected that Mr Ibbotson may have also suffered from similar levels.
The report said: “It is clear from the symptoms that exposure to CO can reduce or inhibit a pilot’s ability to fly an aircraft depending on the level of that exposure.”
It was also detailed how “poor sealing of the cabin or leaks into the heating or ventilation system from the exhaust” can allow gas into the cabin of the plane.
It is currently unknown whether the pair passed out and died on the plane due to their exposure to the deadly gas, or whether they perished on impact with the English Channel.
However, the findings could explain how Mr Ibbotson lost control of the plane.
The AAIB have not added any further details, claiming: “When our investigation has concluded, we will publish a final report.”
Sala was travelling to Cardiff shortly after completing a £15million transfer to former Premier League club Cardiff.
He had returned to former club Nantes to retrieve his belongings and say farewell to staff and teammates.
Guernsey Police launched an immediate search in a bid to find the duo, but the operation was later called off when nothing was found.
UK Air Accident Investigation Branch later launched an official search alongside a second, private underwater search lead by Mearns.
Sala’s body was recovered on February 6 after search teams finally found wreckage but the body of Ibbotson was never found.
An inquest on February 11 was told that the footballer had died from injuries to his head and upper body.
Meanwhile, A couple are currently facing jail after accessing CCTV footage of Sala’s post-mortem.
Sherry Bray, 48, and Christopher Ashford, 62, appeared at Swindon Crown Court on August 9 and were warned they face jail after admitting the charge.
A photo of Sala’s body was reportedly posted online with police launching an investigation.
Bray, of Corsham, was summonsed to court for three counts of computer misuse, perverting the course of justice and sending an indecent or offensive message.
Ashford, of Calne, was summonsed in relation to six counts of computer misuse.
Tributes poured in from across football as Cardiff and Nantes mourned the loss of the striker.
His funeral took place on February 16 in his home town of in Progreso, Argentina.
Sala’s father Horacio tragically passed away three months later after suffering a heart attack.
Prior to his death, he criticised Cardiff for leaving their son “like a dog” following the transfer.
“With all the money that had been paid for him, why was it so hard for them to find something safe? Why couldn’t they?
“But they left him alone. They left him like a dog. They left him, they abandoned him.”
Sala is believed to have not been in favour of his transfer to Cardiff.
A WhatApp message sent by Sala to a friend on January 6 and released by the L’Équipe Enquete documentary in May, have shown that the Argentine – despite admitting it was a good offer financially – was not keen on the move to Cardiff.
“Last night, I sent a message to Meïssa [N’diaye, Sala’s agent], he called me a few hours later,” begins Sala.
“So we had discussions and he told me the last night Franck Kita [son of Nantes owner Waldemar] sent him a message to talk, so he called him. They spoke. And, they want to sell me.
“So, there is the offer from Cardiff today. On their side, they have negotiated to get a lot of money. So they absolutely want me to go there.
“It is true that it is a good contract but from a football perspective it is not interesting for me. So… there you go, they are trying in every way to get me to go there.
“Me I am not scared to go there, because I have battled throughout my career, so to go there and fight, that does not make me scared.
“On the contrary. But also, I say to myself that Meïssa must find me something better between now and the end of the window. Meïssa has said no to Cardiff because he does not want me to go there.
“He thinks that in terms of football, in terms of where we are today, we are in a position of strength in every which way, in terms of on the pitch, the contract, all of that. But I don’t care about that and I do not want that. I don’t give a f*** about being in a position of strength.
“It is true that I would like to find something interesting in terms of contractually and also from a football perspective, but sometimes you can’t have both. On the other hand, I do not want to speak with Kita, because I do not want to get angry. He is someone who disgusts me when I am face to face with him.
“Him today, he wants to sell me to Cardiff because he has done a super negotiation, he will get the money he wants eh?”
“He, he wants me to go there, he hasn’t even asked what I want… All he cares about is money. So, today, we are like that. A complete mess. So there you go… I don’t know.
“I don’t know what to do because as I said to you it is I who has to get up every day and see the face of this person… But nobody is looking at me… myself… me internally, what I am having to go through.
“So, it is very hard, it is very hard, because I feel like there are not many people who would put themselves in my place.”