BEIJING — Rescuers at a mine in southern China have been offered two million yuan ($310,000) for each worker they pull out alive from a colliery that collapsed at the weekend, state media reported.

Heavy rains have hampered efforts to reach 19 workers trapped underground in the coal mine in Heshan city in Guangxi region, and the official Xinhua news agency said late Wednesday six of those had the "highest chance of survival."

The report said local authorities had announced the reward, in an apparent incentive for rescuers, and quoted the Guangxi Heshan Coal Mining Company that runs the colliery as apologising for the accident.

Rescuers have already retrieved three bodies from the scene, and the report said the victims' families had signed compensation deals with the mining company, expected to be around 400,000 to 600,000 yuan.

The accident is just one in a series to have hit China in recent days.

At least 28 people are currently trapped in a coal mine in the eastern province of Shandong after a fire broke out underground on Wednesday evening, a separate Xinhua report said.

The nation's work safety administration initially said 36 people had been trapped by the blaze. But according to the report, some miners had since managed to escape.

In the southwestern province of Guizhou, meanwhile, rescuers were still battling to save 23 miners trapped in another coal mine that flooded on Saturday, the local government said Wednesday.

China's coal mines have a notoriously poor safety record, which the government has repeatedly pledged to address.

In 2010, 2,433 people died in coal mine accidents in China, according to official statistics -- a rate of more than six workers per day.

Labour rights groups, however, say the actual death toll is likely much higher, partly due to under-reporting of accidents as mine bosses seek to limit their economic losses and avoid punishment.