Rescuers on Sunday managed to put out a massive fire triggered by an explosion at a chemical plant in Shanxi province's largest chlor-alkali production base that killed four workers and injured 37 others on Saturday.

A glimpse of the Yushe Chemical Engineering Company plant where an explosion occurred on Saturday, killing four workers, in Yushe county, Shanxi province.

It took more than 100 firefighters a marathon 14 hours to put out the fire, which completely gutted the four-story Yushe Chemical Engineering Company plant, where some 2,700 people are employed, in the province's Yushe county.

The company's factories have been sealed off for the police "to investigate the cause of the incident", police told China Daily on Sunday.

The explosion that occurred at 7:10 pm on Saturday left three workers dead on the scene while the body of the fourth victim was recovered on Sunday morning.

Ren Li, 26, who was working in an adjacent plant, said: "It was like an earthquake. There was a big bang. I ran out of the plant immediately even though my legs were hurt because of the broken glass."

The local government said, of the 37 workers hospitalized, 34 were wounded by broken glass.

As of midday on Sunday, most of the injured workers had been discharged from hospital.

Hao Xiaohu, a doctor at the county hospital, said three of the injured were still lodged in the intensive care unit.

Residents of Nanxiangyang village, a stone's throw from the plant, said they fled their homes following the explosion fearing more blasts and the presence of toxic gas.

"I was lucky I didn't get hurt," said 47-year-old Lian Xinglong, whose roof was dented due to the intensity of the explosion.

"But as you can see, my house is not safe to live in now. I'm thinking of moving into my daughter's house."

The county government on Sunday reiterated on its website that "the provincial environment bureau has found no substance exceeding (intolerable) standards in the air of the factory zone, and the factory has not discharged waste water after the blast".

Footage from the China Central Television showed thick fume rising up from the fire, with the broadcaster saying it was coming out of "a broken chlorine pipe".

The latest government announcement added, "No polyvinyl chloride (PVC, a plastic product) was detected in the air of neighboring villages. Water quality of the local Zhanghe River runs up to the standards and the environment is basically not affected."

Zhang Bo, a police official with the county's public security bureau, said that villagers living nearby returned home after an environmental assessment proved the area was safe to live in.

However, Liu Zili, a senior consultant from Golder Associates, a global company providing consulting services in the areas of geotechnics and the environment, said a conclusion has yet to be summarized based on comprehensive monitoring of the emission density in the affected area.

"Indeed, chlorine is toxic to respiratory tracts for a few days. However, it would have an enduring effect when it contacts soil and water to form an organic compound containing chlorine, which is normally carcinogenic."