The death toll from a highway collapse in southern China's Guangdong province has risen to 48, authorities said, adding dozens of others were injured.

The government said 23 vehicles had been found in a pit after a 17.9-metre-long section of the highway gave way at about 2 am [local time] on Wednesday.

The ground beneath the highway appeared to have caved in, along with the section of the road above it.

Witnesses told local media they heard a loud noise and saw a wide hole open up behind them after driving past the section just before it collapsed.

Video and photos in local media showed smoke and fire at the scene, with highway guardrails slanting down into the flames. A pile of blackened cars could be seen on the slope leading down from the highway.

More disasters likely

Parts of Guangdong province have seen record rains and flooding in the past two weeks, as well as hail. A tornado killed five people in Guangzhou, the provincial capital, last weekend.

Some villages in Meizhou flooded in early April, and the city had seen heavy rain in recent days.

Last month, massive downpours in a different part of the province sparked floods that claimed four lives and forced the evacuation of over 100,000 people.

And a tornado killed five people when it ripped through the megacity of Guangzhou last week.

With rainfall expected to intensify throughout May, the government has warned of possible further disasters.

"Multiparty discussions and evaluations indicate that strong convection and heavy precipitation may increase in China in May," Xinhua cited the emergency management ministry as saying.

The country's lush southern and southeastern provinces — including Guangdong — are likely to be among the worst hit, leading to "a higher risk of geological disasters", the ministry was quoted as saying.