Authorities have pulled more bodies from a massive blast site in the Chinese port of Tianjin, pushing the death toll to 112 as teams scrambled to clear dangerous chemical contamination.

Hundreds of people were injured and 85 firefighters and 10 others are missing since a fire and rapid succession of blasts late on Wednesday hit a warehouse for hazardous chemicals in a mostly industrial area of Tianjin, 120 kilometres east of Beijing.

By today, authorities confirmed there were "several hundred" tons of the toxic chemical sodium cyanide on the site at the time of the blasts, although they said there have not been any devastating leaks.

Sodium cyanide is a toxic chemical that can form a flammable gas upon contact with water. Earlier state media reports said the warehouse was storing 700 tons of the chemical - 70 times more than it should have been holding at one time.

Angry relatives of the missing firefighters and local residents whose homes were destroyed by the blasts showed up at a government news conference to demand information and accountability.

The death toll includes at least 21 firefighters - making the disaster the deadliest for Chinese firefighters in more than six decades. About 1,000 firefighters responded to the disaster, and 85 of them remained unaccounted for on Sunday.

The public has raised concerns whether firefighters were put into harm's way in the initial response to the fire and whether the hazardous material - including compounds combustible on contact with water - was properly taken into account in the way the firefighters responded.

The massive explosions happened about 40 minutes after reports of a fire at the warehouse and after an initial wave of firefighters arrived and, reportedly, doused some of the area with water.

Outside the Mayfair Hotel where the authorities hold regular news conferences, a woman pleaded for information on her husband.

"(They) have said nothing. We know nothing," the woman said. "We've been told nothing."

Another man demanded information from a government official. "We've been here for three days and we've not had one piece of information," he said.

Local officials have been hard-pressed to explain why authorities permitted hazardous goods warehouses so close to residential complexes and critical infrastructure, clearly in violation of the Chinese rule that "hazmat" storage should be 1,000 metres away from homes and public structures.

Homeowners of the nearby Qihang residential compound unfurled banners demanding government accountability and proper compensation for their damaged homes. Many were wearing masks, and some had bandages, possibly over cuts.

Shi Luze, chief of staff for the People's Liberation Army's Beijing district, said authorities believe there were "several hundred" tons of cyanide at the warehouse. He said that leaked chemicals were being neutralised and those still in packages removed from the site.

He also said that 3,000 soldiers had been dispatched to the disaster zone to clean up any leaks of hazardous materials.

Authorities temporarily detected the highly toxic hydrogen cyanide in the air slightly above safety levels at two locations, Tianjin environmental official Bao Jingling told a news conference. The contaminationyesterday afternoon, at four per cent and 50 per cent above the safety level, was no longer detectable later, Mr Bao said. "These levels are actually very low," he said. Mr Bao said the cyanide was yet to be detected in water samples.

Authorities were keeping residents, journalists and other people not involved in the disaster response outside a 3km radius around the site of the explosions in what media reports said was an operation to clean up the sodium cyanide.

Rescuers pulled out a survivor from a shipping container on Saturday, state media reported. Footage showed the 56-year-old man being carried out on a stretcher by a group of soldiers wearing gas masks. He remained in critical condition today, local media reported.

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