Argentine soccer player Emiliano Sala’s blood showed high levels of carbon monoxide, air accident investigators have said.
They believe it was likely the pilot of the plane flying him to Britain had also been exposed before their fatal crash.
Sala (28) was being flown from his previous club Nantes in western France to Wales to join Cardiff City when the Piper Malibu aircraft disappeared over the English Channel in January.
His body was recovered when the wreckage of the plane was finally found about two weeks later.
A special bulletin from Britain’s Air Accident Investigation Branch (AAIB) said toxicology tests on his blood had shown that Sala had a saturation level of 58pc of carboxyhaemoglobin (COHb), a mixture of carbon monoxide (CO) and hemoglobin.
Exposure to carbon monoxide can lead to damage to the brain, heart and nervous system and a COHb level of over 50pc is considered to be potentially fatal, causing seizure, unconsciousness or a heart attack.
“In this type of aircraft, the cockpit is not separated from the cabin and it is considered likely that the pilot would also have been affected to some extent by exposure to CO,” 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.”
Sala’s family said an examination of the wreckage was needed to determine how gas was able to leak, adding: “[It] raises many questions for the family.”
The AAIB said its investigations were continuing.