According to the report by India's Aircraft Accident Investigation Bureau (AAIB), switches in the Boeing 787 Dreamliner's cockpit that controlled fuel moved to a "CUTOFF" position.
It said: "Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of one second.
"The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off."
There was then confusion in the cockpit. In the voice recording, one of the pilots is heard asking the other why he "cut off". The other pilot responds that he did not do so.
The 15-page report did not identify which comments were made by the flight's captain and which were made by the first officer. One of the pilots made a "mayday, mayday, mayday" call just before the crash.
Both pilots were experienced, with around 19,000 flying hours between them, including more than 9,000 on the 787.
img: Prime Minister's Office (GODL-India), GODL-India <https://data.gov.in/sites/default/files/Gazette_Notification_OGDL.pdf>, via Wikimedia Commons