TAIPEI (Taiwan News) — Mechanical failure and turbulence can be 80 percent ruled out as causes of the Black Hawk helicopter crash which killed eight senior military officers, reports said Saturday (Jan. 4).

Chief of General Staff Shen Yi-ming (沈一鳴) and seven others died when their helicopter crashed in an isolated area en route to Yilan County Thursday (Jan. 2) morning. The remaining five other passengers survived.

According to a preliminary investigation by the Taiwan Transportation Safety Board (TTSB), mechanical malfunctions can be nearly ruled out as the cause of the crash, while weather, including turbulence and wind shear, can be 80 to 90 percent ruled out, CNA reported Saturday.

Officials are reportedly still looking at the possibility that human error contributed to the crash.

The TTSB plans to hand over information from the helicopter’s flight recorder, or black box, to the Ministry of National Defense Saturday afternoon.

However, a chip card containing crucial data has been returned to its manufacturer for analysis. The information can account for 100 percent of what went wrong, including instances of mechanical failure or erroneous handling of the chopper, CNA reported a TTSB source as saying.