Weak rock structure was the primary cause of the landslide that occurred on Monday in Zhenxiong county, Yunnan province, resulting in at least 34 deaths, a preliminary investigation revealed on Wednesday.

According to the disaster-responding task force, following on-site investigations and preliminary analyses, a team of experts discovered that the steep terrain and topography provided the conditions necessary for the landslide to occur, while the layered and fractured rock structure was the "main internal and objective factor" leading to the landslide, the team said in a news release.

Furthermore, prior rainfall in the area softened the weak planes within the rock mass, it said, noting that the rainy and snowy weather before the landslide led to the enrichment of groundwater, ultimately reaching a critical point that triggered the landslide.