TAIPEI — Thick fog and human factors were to blame for a military helicopter crash in January that killed Taiwan's chief of general staff and seven senior officers, according to investigators who ruled out mechanical failure.

"Weather, terrain and human factors were behind the crash," Air Force Major General Huang Chih-wei told reporters at a press conference on Saturday.

"The pilot had only six or seven seconds to pull up after thick fog rapidly descended," Huang added.

In the preliminary investigation report, the co-pilot had warned about the helicopter's altitude twice before it crashed onto a mountain slope.

The 62-year-old military chief General Shen Yi-Ming and his entourage were on a routine mission to visit soldiers in northeast Yilan county for the upcoming Lunar New Year when the incident happened.

The UH-60M Black Hawk helicopter was carrying 13 people in total, with five surviving the crash. It disappeared from radar less than 15 minutes after taking off, and did not send a distress call.

There have been a number of incidents involving Taiwan's 60 Black Hawk helicopters — purchased from the United States — in recent years.

In 2018 a chopper belonging to a government rescue agency crashed during a medical mission off outlying Orchid Island, killing six people on board in an incident attributed to human error.

There were also two crash landings in 2016 and 2018 with no casualties.

"We will be looking into future adjustments in our pilot's simulator training after this accident," Huang said. — AFP