Hundreds of tonnes of highly toxic sodium cyanide were being stored at the warehouse devastated by two giant explosions in the Chinese port of Tianjin that killed 112 people, a senior military official says.

The comments by Shi Luze, chief of the general staff of the Beijing military region, were the first official confirmation of the presence of the chemical at the hazardous goods storage facility at the centre of the blast.

Nearly 100 people remain missing, including 85 firefighters, though officials cautioned that some of them could be among the 88 unidentified corpses so far found.

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More than 700 people have also been hospitalised as a result of Wednesday’s blasts — which triggered a huge fireball and a blaze that emergency workers have struggled to put out since then, with fresh explosions on Saturday.

Eighty-five of the dead were firefighters, Xinhua said, including 72 who worked for the Tianjin Port Group.

General Shi told a news conference that cyanide had been identified at two locations in the blast zone.

“The volume was about several hundreds of tonnes according to preliminary estimates,” he said, adding that workers were trying to clear the area of chemicals before possible rain showers, which could create toxic gas.

Wednesday’s blasts were so large they were seen by satellites in space and registered on earthquake sensors.

Shockwaves from the explosions were felt by residents in apartment blocks kilometres away in the city of 15 million people.

Aerial footage of the blast zone shows scenes of monumental devastation, with buildings burned out, shipping containers crushed and tumbled like piles of children’s blocks, and fields of burned-out vehicles.

After the event: damage from Tianjin explosion.

Officials insist Tianjin’s air is safe to breathe

On Saturday, China evacuated residents who had taken refuge in a school near the site of the blasts after a change in wind direction prompted fears toxic chemical particles could be blown inland.

Officials have insisted that despite the presence of some pollutants at levels above normal standards, the air in Tianjin remains safe to breathe, but some police and other personnel at the scene have been seen wearing gas masks or full protection suits.

“I can responsibly say that there will be no secondary damage to the people,” General Shi said, referring to people outside the evacuation zone.

Officials have listed a litany of chemicals that may have been at the warehouse, but have been unable to say precisely which ones were present.

Sodium cyanide specialists and soldiers trained in anti-chemical warfare techniques were deployed to the site on Saturday and have used hydrogen peroxide, which neutralises sodium cyanide.

Chemical experts have also questioned whether water hosed on the burning warehouse by firefighters could have contributed to the explosions.

Calcium carbide, one of the chemicals that police say was listed at the warehouse, can react with water to create acetylene, a highly explosive gas.

David Leggett, a chemical safety expert based in California, said an acetylene explosion could have detonated ammonium nitrate, which had also been stored in the warehouse.

Xinhua identified the owner of the warehouse as Tianjin Dongjiang Port Ruihai International Logistics and the China Daily newspaper said its manager had been detained.

Some 6,300 people have been displaced by the blasts, Xinhua said earlier.

China has moved to limit criticism of handling of the disaster, blocking some critical posts on social media, and suspending or shutting down more than 360 social media accounts.

A total of 50 websites have also been punished for “creating panic by publishing unverified information or letting users spread groundless rumours”, according to the Cyberspace Administration of China.