Premier League footballer Emiliano Sala and his pilot were exposed to high levels of carbon-monoxide inside their private plane minutes before it crashed.
Air accident investigators said the gas levels were enough to cause seizures, unconsciousness and a heart attack.
The light aircraft crashed into the Channel on January 21st.
Argentinian Sala was on his way to join Cardiff City after signing for £15 million from French club Nantes.
Investigators are trying to find how the noxious gas found its way into the plane’s cabin.
The Air Accidents Investigation Branch added: “Work is also continuing to investigate pertinent operational, technical, organisational and human factors which might have contributed to the accident.”
Daniel Machover, lawyer for the Sala family, said: “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.
“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.
“Emiliano’s family call on the AAIB to salvage the wreckage of the plane without further delay.”
