Work safety inspectors are to be sent undercover at production bases nationwide this month as part of strict measures to expose hazards.

Sun Huashan, deputy head of the State Administration of Work Safety, said on Tuesday that authorities at all levels will strengthen supervision to prevent workplace accidents as 2017 draws to a close.

The main focus will be coal mines, chemical plants and firework factories, he said.

"Strong supervision can push enterprises to take responsibility in guaranteeing safe production," Sun said. "We will carry out more and stricter undercover investigations."

Accidents, such as fires and chemical leaks, often happen toward the end of the year due to the cold, dry weather, he said, explaining that low temperatures can open cracks in pipelines.

Safety authorities will also improve emergency response and rescue capabilities, Sun said. "In the long run," he added, "in some high risk industries we will replace people with machines to insure safe production."

According to the State Council's Commission for Safe Production, 31,000 enterprises that failed to meet safety standards were closed in the most recent round of national inspections, which lasted from July to October.

Over 3,500 people were investigated on suspicion of criminal behavior, with fines totaling 2.8 billion yuan ($423 million), the commission said.