Malaysian-airlines-777A Malaysian official told reporters Friday night that the missing Malaysia Airlines jet that disappeared over the waters of the Gulf of Thailand was hijacked.

The unnamed official said a hijacking was no longer just one of the many theories about what happened to the missing plane but is now conclusive, the Associated Press reports.

One or more hijackers that had significant experience as a pilot, took control of the plane, switching off communications devices and steering it off course, investigators have concluded.

The timing of signal failures is a crucial piece of evidence that led investigators to conclude that the plane was hijacked. The plane’s identifying transponder stopped working more than 10 minutes before the plane’s messaging system failed. A gap as big as this eliminates possibility of a sudden, catastrophic event.

According to the Malaysian government, hijacking is now the definite conclusion about what happened to Malaysia Airlines Flight 370, which went missing on March 8. However the questions of who was behind it and why remain a mystery.