At least 91 people were still missing after 33 buildings collapsed in a landslide Sunday in southern China. Premier Li Keqiang ordered an investigation into the mudslide that toppled Hengtaiyu Industrial Park in Shenzhen, which sits just across the border from Hong Kong. The mud covered more than 94 acres and was 11 yards deep in some areas, Shenzhen Vice Mayor Liu Qingsheng told the state-run Xinhua news agency. The ministry of land resources blamed the calamity on a nearby mountain of waste construction mud. About 900 people were evacuated as the landslide smashed into buildings and a section of China’s West-East natural gas pipeline in the vicinity also burst, Xinhua reported. It’s unclear if the explosion had any impact on the landslide.