A collapse of an expressway section in China's Guangdong province caused vehicles to plunge and killed 36 people while injuring another 30, state media reported on Thursday, as millions in the country travel for the May Day holiday break.

The collapse, triggered by heavy rain, occurred at around 2:10am on Wednesday on the Meizhou-Dabu Expressway, Xinhua news agency reported, adding that the collapsed section was 17.9 metres in length and caused 23 vehicles to plunge.

Meizhou is one of the areas in southern China's Guangdong that has been badly hit by heavy rain and hail since late April which set off dangerous mudslides, inundated homes and destroyed bridges.

President Xi Jinping called for the utmost efforts to save lives and eliminate dangers as the rainy weather continued in the region, according to a Xinhua report.

Task forces from the central and local governments have been dispatched for the rescue work, the report added.