The crash took place on a highway in rural Guizhou province when the vehicle carrying 47 people in total “flipped onto its side”, Sandu county police said in a statement published on social media.

The remaining 20 people were being treated for injuries and emergency responders were dispatched to the scene, police said, without providing any more details.

The accident happened in Qiannan prefecture – a poor, remote and mountainous part of Guizhou, home to several ethnic minorities.

Two social media posts, that have since been deleted, by the China Road Network monitoring service said that the accident occurred at around 2:40 am (1840 GMT on Saturday), according to screenshots circulating on the Twitter-like Weibo.

Social media users angrily demanded why a passenger bus was travelling down a highway in the early hours of the morning, when many major roads in the province have been closed to regular traffic.

One hundred toll stations are shuttered in Guizhou because of Covid-19 restrictions and long-distance passenger journeys across China are banned from running between 2:00 am and 5:00 am.

Guizhou is in the midst of a Covid outbreak that has seen over 900 new infections in the past two days alone.

Its provincial capital Guiyang, home to six million residents, was locked down earlier in September.

The bus was travelling southwards in the direction of Guiyang to Libo county, according to the police statement.

Road accidents remain fairly common in China, where irregular enforcement and lax safety standards have resulted in a string of fatalities over the years.

In June, a driver was killed after a high-speed train derailed in Guizhou province.

And in March a Chinese passenger jet crash killed all 132 people on board, marking the deadliest aviation accident to take place in China for decades.