Footballer Emiliano Sala was exposed to high levels of carbon monoxide prior to a fatal plane crash in the English Channel, a report has revealed.
Sala, 28, and pilot David Ibbotson crashed on 21 January while travelling to Cardiff from Nantes in France.
Toxicology tests on Sala’s body showed CO levels in his blood were so great it could have caused a seizure, unconsciousness or a heart attack.
The Sala family’s lawyer said the report raised further questions.
Mr Ibbotson, from Crowle, North Lincolnshire, has still not been found, but it is likely he would also have been exposed to carbon monoxide, the Air Accidents Investigation Branch (AAIB) report said.
Sala’s blood had a COHb (carboxyhaemoglobin – which forms in red blood cells upon contact with carbon monoxide) level of 58%.
At this level, symptoms would include include seizure, unconsciousness and heart attack, the report said.
It added: “A COHb level of more than 50% in an otherwise healthy person is generally considered to be potentially fatal.”
Piston engine aircraft such as the Piper Malibu involved in the crash produce high levels of carbon monoxide, the report said.
The gas is normally conveyed away from the aircraft through the exhaust system, but poor sealing or leaks into the heating and ventilation system can enable it to enter the cabin.
Several devices are available to alert pilots over the presence of carbon monoxide.
The AAIB said they are not mandatory but can “alert pilots or passengers to a potentially deadly threat”.
Daniel Machover of Hickman & Rose solicitors, who represents the Sala family, said: “The family believe that a detailed technical examination of the plane is necessary.
“The family and the public need to know how the carbon monoxide was able to enter the cabin. Future air safety rests on knowing as much as possible on this issue.”
AAIB investigators are working with aircraft manufacturers in the USA – where the Piper Malibu was registered – to look at ways carbon monoxide could have entered the cabin.
They are looking at how “operational, technical and human factors” could have contributed to the crash and warned the aviation community about potential dangers.
In a statement, Cardiff City said it was “concerned” by the report, adding: “We continue to believe that those who were instrumental in arranging its [the plane’s] usage are held to account for this tragedy.”
In an interview in February, football agent Willie McKay, who commissioned the flight, told the BBC he and his family paid for the flight.
He was not involved, he said, in selecting the plane or the pilot and it was not a cost-share arrangement.
Geraint Herbert, the AAIB’s lead inspector for this investigation, said it is believed both men were exposed to the gas before the plane crashed.
“Symptoms at low exposure levels [to carbon monoxide] can be drowsiness and dizziness, but as the exposure level increases, it can lead to unconsciousness and death,” he added.
“The investigation continues to look into a wide range of areas in relation to this accident, but in particular we are looking at the potential ways in which carbon monoxide can enter the cabin in this type of aircraft.”
The investigation into the crash is ongoing and is not expected to report its full findings until early 2020.
The bulletin – the second to be released following the crash – highlights the dangers of exposure to carbon monoxide in piston and turbine engine aircraft.
The plane carrying the Argentine striker – Cardiff City’s £15m record signing – lost contact with radar near Guernsey.
Sala signed for Cardiff on 19 January – just two days before the crash – and had returned to Nantes to say goodbye to his former teammates.
An official search was called off on 24 January after Guernsey’s harbour master said the chances of survival were “extremely remote”.
But an online appeal started by Sala’s agent raised £324,000 (371,000 euros) for a private search, led by marine scientist and oceanographer David Mearns.
Sala’s body was recovered from the wreckage of the Piper Malibu N264DB on 7 February and subsequently repatriated to Argentina.
Mr Ibbotson has still not been found, but it has since been discovered he was not qualified to fly at night.
Details released about Mr Ibbotson on Wednesday showed he had about 3,500 hours of flying experience – of which 30 were flying similar types of aircraft.
He had flown for about 20 hours in the 90 days before the crash, and seven hours in the previous 28 days.
Since Sala’s death, Nantes and Cardiff City have been involved in a dispute over the transfer fee after the Welsh club claimed the deal was not legally binding.
Sala’s family and friends claimed he was “abandoned like a dog” before his death.
His father Horacio died in April, three months after his son, after suffering a heart attack at home in Progreso, Argentina.