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.

Dialogue heard on a cockpit voice recording indicates that the captain of the Air India flight that crashed in June, killing 260 people, may have turned off the fuel just after takeoff, prompting the first officer to panic, according to The Wall Street Journal, which cited sources familiar with U.S. official's early assessment.