Six people died and four are missing after a bus plunged into a sinkhole on a busy road in northwestern China on Monday afternoon. The road collapsed at about 5.30pm as passengers prepared to board the bus outside Changcheng Hospital in Xining, Qinghai province, according to the city government. Footage of the incident circulating online indicated that the collapse was followed by an explosion and heavy smoke from inside the hole. It was not clear how many people were on the bus. Sixteen people injured in the incident were in a stable condition in hospital. Among the injured was a boy who pushed a child out of danger before going to the aid of others and then falling into the hole, Shanghai-based news service Thepaper.cn quoted a municipal employee as saying. The sinkhole was 80 square metres (860 sq ft) in area and an investigation into its cause was under way. The municipal government said on Tuesday morning that authorities were trying to identify the six bodies recovered from the site. In July last year, a woman died after she and her husband were swallowed by a sinkhole in a road in Tangshan, Hebei province. And in October 2018 a road collapsed in Dazhou, Sichuan province, killing four people. Purchase the China AI Report 2020 brought to you by SCMP Research and enjoy a 20% discount (original price US$400). This 60-page all new intelligence report gives you first-hand insights and analysis into the latest industry developments and intelligence about China AI. Get exclusive access to our webinars for continuous learning, and interact with China AI executives in live Q&A. Offer valid until 31 March 2020.