A cockpit voice recording of doomed Air India Flight 171 indicates the younger co-pilot asked his more experienced colleague why he turned off the plane’s fuel-supply switches, according to people familiar with the matter.

According to a report published on Wednesday by The Wall Street Journal quoting sources close to United States officials’ early assessment of evidence, the black box audio recording of the last conversation between the two pilots indicates that the captain might have turned off the switches controlling the flow of fuel to the plane’s engines.

The captain of the crashed Air India jet likely cut off the fuel supply before it crashed in Ahmedabad, US officials believe.