Hundreds of tonnes of highly poisonous cyanide were being stored at the warehouse that was devastated by two giant explosions in the Chinese port of Tianjin, a senior military officer said yesterday.
The comments by Mr Shi Luze, chief of the general staff of the Beijing military region, were the first official confirmation of the presence of the chemical in the hazardous goods storage facility at the centre of the blast.
With fresh explosions on Saturday, the disaster has raised fears of toxic contamination.
Residents and victims' families have criticised the authorities for an "information blackout" as China suspended or shut down dozens of websites for spreading "rumours".
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.
More than 700 people have also been hospitalised as a result of Wednesday's blasts, which killed 112.
Mr Shi, a general, 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.
A military team of 217 chemical and nuclear experts was deployed early on, and earlier Chinese reports said 700 tonnes of sodium cyanide were at the site.
Officials have called in experts from producers of the material to handle the situation and the neutralising agent hydrogen peroxide has been used.
According to the US Centers for Disease Control and Prevention, exposure to cyanide can be "rapidly fatal."
Authorities have repeatedly sought to reassure the public, insisting that despite the presence of some pollutants at levels above normal standards, the air in Tianjin remains safe to breathe.
Chinese Premier Li Keqiang arrived in Tianjin yesterday afternoon to direct rescue efforts, a move often made after major disasters in the country, official media reported.
Pictures showed the Communist Party number two within a kilometre of the blast site, dressed in an ordinary white shirt and not wearing a mask.
But the official Xinhua news agency reported late Saturday that cyanide density in waste water had been 10.9 times higher than the standard level on the day following the explosions. It has since fallen but was still more than twice the normal limit.
Environmental campaign group Greenpeace said yesterday it had tested surface water for cyanide at four locations in the city and had not detected high levels of the chemical.
But it reiterated its call for comprehensive tests on the air and water and for the results to be published.
Yesterday, AFP saw young men who were carrying personal belongings leaving FAW Toyota apartments and boarding a bus which will take them to alternative accommodation.
Police with face masks could be seen at one checkpoint.
Mr Steve Ra, an American who was evacuated by his employer to another part of Tianjin, said he was worried about the potential health effects of the blast.
"The main concern is just the air," Mr Ra told AFP. "I'm waiting to go back to get my normal life back. But I don't know what I'll be breathing so that's the biggest concern."
Tianjin residents, relatives of the victims and online commentators have slammed local authorities for a lack of transparency, and even tried to storm a news conference on Saturday.
Yesterday, sobbing men confronted security at the hotel where officials have been briefing journalists, with one shouting "Police, I will kill someone" in what appeared to be a desperate bid to draw attention before being comforted by a policeman.
Another lashed out at reporters attempting to photograph him, saying: "Don't take my photo, it is useless. The news has no truth!" Outside the conference, residents of a building damaged by the blasts held a protest.
The government has moved to limit criticism of the handling of the aftermath, with a total of 50 websites shut down or suspended for "creating panic by publishing unverified information or letting users spread groundless rumours", according to the Cyberspace Administration of China.
Critical posts on social media have also been blocked, and more than 360 social media accounts have been punished.
One post on microblogging platform Sina Weibo said: "Why is it 'rumours' are flying everywhere every time there is a disaster? Are they really rumours? The government is lying... You have lied to the people too much and made yourself untrustworthy."
This article was first published on August 17, 2015.
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