At least 33 people were trapped after a gas explosion ripped through a coal mine in southwestern China's Chongqing on Monday, Chinese media reported.

The blast reportedly took place at 11:30 a.m. at the Jinshangou Coal Mine in the town of Laisu. There were allegedly 35 miners working in the shaft, and only two were rescued so far, according to state-backed Xinhua News agency.

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Meanwhile, rescue operations are ongoing, although the condition of the victims trapped inside cannot be confirmed, a local government official who refused to be named said.

Such accidents usually result when a flame or electric spark ignites leaking from the coal seam, the Seattle Times noted. An effective ventilation system is supposed to prevent gas from being trapped.

Just last month, a coal mine-related gas explosion in the city of Shizuishan in the western region of Ningxia also killed at least 20 workers. Initial investigations revealed that illegal mining was the cause of the explosion.

On the other hand, a study by Greenpeace found that between January and August, more than 200 people died in chemical-related accidents in China, suggesting that China's chemical industry remained lax even after the deadly explosion in the port city of Tianjin last year that killed at least 165 individuals, injured 800, and caused an estimated $1.1 billion damage to the city.

Cheng Qian, a Greenpeace activist, is encouraging the government to "take urgent action to manage chemicals in a sound manner, provide a safety net for workers and citizens, and protect ecologically important areas across the country."

Tagscoal explosion, coal mine, Gas Explosion, Chinese coal mine, explosion accidents, Chongqing