In a string of recent collapses in China, at least six people have been dead and 16 others injured after a massive sinkhole opened up and swallowed a bus and pedestrians in the city of Xining in Qinghai province.

According to the state news agency Xinhua, a public bus had just halted at a stop on Monday afternoon when a gaping sinkhole suddenly opened up underneath it and swallowed the bus.

Authorities said more than 1,000 emergency workers attended the scene at about 5.30 pm and rescuers searched for four missing people, while the injured were taken to hospital for treatment.

According to state media, the sinkhole stretched nearly 10m (32 feet) in diameter.

It is unclear how many people were inside the bus at the time of the incident. The cause of the incident is being investigated, the state-run broadcaster CCTV said.

Pictures of the road collapse outside a hospital showed the vehicle almost entirely underground near a bus stop as people ran for safety.

Back in 2016, at least three people fell into a huge sinkhole in central Henan province, which swallowed a section of road and passersby. And in 2013, five people died when a 10m (33ft) wide sinkhole opened up at the gates of an industrial estate in Shenzhen.