Soccer player 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 and pilot David Ibbotson crashed on January 21 when they went to Cardiff from the French city of Nantes.
Toxicology tests on Sala's body showed that the CO levels in his blood were so large that it could have caused a seizure, unconsciousness or a heart attack.
Mr. Ibbotson, from Crowle, North Lincolnshire, has still not been found
But it is likely that he would also have been exposed to carbon monoxide, said the Air Accidents Investigations Branch (AAIB) report.
Sala's blood had a COHb (carboxyhemoglobin) level of 58% – a level at which symptoms include seizures, unconsciousness and heart attack, the report said.
It said: "A COHb level of more than 50% in an otherwise healthy person is generally considered potentially fatal."
Geraint Herbert, AAIB head of aviation accidents, said it was 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 when exposure levels increase, it can lead to unconsciousness and death," he added.
"The investigation continues to investigate a wide range of areas associated with this accident, but we are looking in particular at the potential ways in which carbon monoxide could enter the cabin of this type of aircraft."
Attorney for the Sala family, Daniel Machover of Hickman & Rose attorneys, said the report raised further questions.
"The family believes that a detailed technical examination of the planet is necessary," he said.
"The family and the public need to know how carbon monoxide could get into the cabin. Future aviation safety is based on knowing as much as possible about this issue."
The aircraft carrying the Argentine striker – Cardiff City's record-breaking £ 15 million signing – flew in lost contact with radar near Guernsey.
Sala signed for Cardiff on January 19 – just two days before the crash – and had returned to Nantes, in northwestern France, to say goodbye to his former teammates.
An official search was interrupted on January 24 after Guernsey's harbor master said the chance of survival was "extremely remote".
But an online appeal started by Sala's agent raised £ 324,000 (€ 371,000) for a private search, led by marine researcher and oceanographer David Mearns.
Sala's body, recovered from the wreck of Piper Malibu N264DB following a privately funded search on February 7, was returned to Argentina.
Mr. Ibbotson has still not been found, but it has since been discovered that he was not qualified to fly at night.