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Authorities ordered the evacuation of a 1.8-mile zone around the Chinese port city of Tianjin on Saturday as fresh explosions were heard and fires continued to rage — and the death toll rose to 104.

The new toll from Wednesday's huge blasts, at a warehouse storing hazardous materials, includes at least 21 firefighters, state media said.

Rescuers also found an additional survivor Saturday as authorities evacuated much of the area to clean up dangerous chemical contamination. Several additional small explosions rocked the disaster zone as the clean-up continued.

Police have, for the first time, confirmed the presence of deadly sodium cyanide — fatal when ingested or inhaled, the state-run Beijing News said.

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Police and military staff were deployed at checkpoints leading to the explosion site, and helicopters were hovering above.

"I do feel a bit afraid," said construction worker Li Shulan, 49, when asked about the air quality. "It definitely doesn't feel good. As you can see our boss is making us wear masks."

A huge hole is seen at the core area of Tianjin blasts in this aerial photo. Xinhua

A retired environmental official told reporters that air pollution posed no risk. "At the moment, the (air pollution) does not pose much danger to those in the vicinity," said Bao Jingling, a former engineer with the city's environmental protection bureau.

Harmful substances could not be detected in the air from 17 monitors placed around the city, said Bao.

About 6,300 people have been displaced by the blasts, with around 721 injured and 33 in serious condition, Xinhua news agency said. Shockwaves from the explosions were felt by residents in apartment blocks miles kilometers away in the city of 15 million people.

About a dozen family members of missing firefighters tried to storm a news conference, angry at a lack of information about their loved ones.

"We have gone to each and every hospital by ourselves and not found them," said Wang Baoxia, whose elder brother is missing.

"There is no government official willing to meet us. Not even one," she said. Relatives said around 25 fire fighters they said were missing were young contract workers not part of official city fire brigades.

Media have said such fire fighters in China, often only on two-year contracts, lack training as new recruits.