Footballer Emiliano Sala was exposed to high levels of carbon monoxide before his plane crashed into the sea, investigators said Wednesday.
Toxicology tests found that the star had a high saturation level of COHb (the combination product of carbon monoxide and haemoglobin), Britain's Air Accident Investigation Branch (AAIB) said in an update.
"It is considered likely that the pilot would also have been exposed to carbon monoxide," it said in a Special Bulletin. "This ... highlights the danger of exposure to carbon monoxide in both piston and turbine engine aircraft."
The Argentine striker was en route from Nantes, France, to Cardiff, Wales, in January to begin a new chapter in his career when the single-engine Piper Malibu aircraft he was aboard crashed into the English Channel.
A funeral was held in Sala's hometown of Progreso, Argentina, after his body was recovered from the sea bed.
"Piston engine aircraft produce high concentrations of CO that are conveyed away from the aircraft through the exhaust system," Wednesday's Special Bulletin said. "Poor sealing of the cabin or leaks into the heating and ventilation system from the exhaust can provide pathways for CO to enter the cabin. Whilst piston engines produce the highest concentration of CO, exhausts from turbine engines also contain CO."
Exposure to CO can "reduce or inhibit a pilot's ability to fly an aircraft depending on the level of exposure," it said.
The AAIB is "working with the aircraft and engine manufacturers and the National Transportation Safety Board (NTSB) in the USA to identify possible pathways through which CO might enter the cabin of this type of aircraft," it added.
Sala's family said a detailed examination of the plane wreckage was needed to determine how the gas was able to leak into the cabin.
"That dangerously high levels of carbon monoxide have been found in Emiliano's body raises many questions for the family. How he died will be determined at the inquest in due course," they said in a statement.
"Future air safety rests on knowing as much as possible on this issue."