According to the coroner, the cause of death was due to asphyxia, or lack of oxygen.

Source: https://newstalk1290.com/ixp/143/p/8-strange-places-where-dead-bodies-have-been-found/

Cahill wrote that Thao "actively encouraged his three colleagues' dangerous prone restraint of Floyd" despite Minneapolis police training that the position could cause asphyxia.

Source: https://theweek.com/crime-and-punishment/1023168/ex-police-officer-convicted-of-aiding-george-floyds-murder

It concluded that he died from asphyxia and drowning.

Source: https://www.dailyherald.com/news/20230731/bartlett-mans-drowning-in-gary-indiana-ruled-an-accident

'They learned that Chauvin was trained against prone restraints because of positional asphyxia, which is the very thing that killed Floyd.

Source: https://www.dailymail.co.uk/news/article-11650229/Derek-Chauvin-appeals-murder-conviction-George-Floyd-case-denied-fair-trial.html?ns_mchannel=rss&ns_campaign=1490&ito=1490