Eight people including the chief of Taiwan’s armed forces were killed Thursday after the military helicopter carrying them crashed on a mountainside during a routine trip, Taiwan’s military said.

The Black Hawk helicopter was carrying 13 people, including Shen Yi-ming, an air force general who served as the chief of general staff of Taiwan’s armed forces. The helicopter left Songshan Airport in Taipei, the capital, shortly before 8 a.m. to fly to Yilan County in northeastern Taiwan for an inspection, the military said.

The last contact with the helicopter was at 8:07 a.m. The military has not yet said what may have caused the crash in a mountainous district southeast of Taipei.