A large sinkhole opened on a busy road in northwest China on Monday, swallowing a public bus and passersby before causing an explosion that killed at least six people. State media later reported at least 15 people were injured and 10 more remain missing.

The incident happened around 5:30 p.m. local time on a heavily trafficked street in Xining, the capital of Qinghai province, state media reports. It marks the latest instance of a sinkhole opening around busy or rapidly developing parts of China.

Video from the scene captured by CCTV and circulating on Chinese social media showed people gathered at a bus stop outside the Great Wall Hospital in the city’s Chengzhong District when the road suddenly buckles, sending people on the street running. Several more people on the street fell into the hole as it widened, swallowing the front end of the bus and a street sign. After a few seconds, the flash of a fiery explosion is seen before yellow smoke pours out of the sinkhole. The sinkhole measured 32 feet wide, state officials told the South China Morning Post.

It’s unclear how many passengers were on the bus, and the deceased have not yet been identified. The incident drew more than 1,000 people and 30 vehicles to the search-and-rescue efforts, the Xinhua News Agency reported, according to Agence France-Presse.

Sinkholes are commonly caused when soft material like limestone, carbonate rock or salt bed erodes beneath the surface; they can occur naturally or be caused by man-made behaviors tied to groundwater pumping or construction, according to the U.S. Geological Survey. In China, mineral and coal mining as well as rapid construction projects are believed to be the causes of the country’s numerous and often deadly sinkholes.

In 2018, four people died after a sinkhole opened up on a busy street in Dazhou, in China’s Sichuan Province. In 2015, five people died after being swallowed by a 32-foot sinkhole in the industrial city of Shenzhen, just outside Hong Kong.

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