The cave-in occurred at around 2am in Dabu County of Guangdong’s northern Meizhou City. Nearly 18 metres (59 feet) of the mountainous highway crumbled into the forested slope below, trapping 18 vehicles and 49 passengers in all, the local government said.
In a statement, it said 30 victims had been sent to hospital, while around 500 public security, emergency response, firefighting, health and sanitation and other workers were taking part in the rescue work. .
The condition of the hospitalised patients was “not life-threatening at the moment”, the statement said, but did not specify the level of their injuries.
The reason for the collapse has yet to be declared and the matter is under investigation.
The accident occurred as China began a five-day break for Labour Day, one of the four major holiday and travel periods for the country when highways are toll-free and see heavy traffic.
The others are Lunar New Year, called Spring Festival in China, the Tomb Sweeping Festival and National Day in October.
Footage and pictures shared by local news outlets showed flames and smoke rising from the collapsed section, while charred cars were visible on the gouged out slope. The stricken highway links Guangdong to southeastern Fujian province.
It is the latest tragedy to hit Guangdong province, which has experienced a string of extreme weather events in recent weeks, from fatal floods to a deadly tornado.
Guangdong authorities warned Wednesday that more heavy rainfall was expected during the holiday, with higher risks of floods and landslides in some areas.
