Pollution fears were growing among the residents of the northern Chinese city of Tianjin on Friday, as the ruling Chinese Communist Party kept a stranglehold on information on suspected dangerous chemicals involved in Wednesday night's massive explosions.
Up to 1,000 firefighters were still struggling to extinguish blazes at the site on Friday, with smoke billowing from three areas, sparking fears over whether more toxic fumes would contaminate the city's air, official media and local residents said.
Environmental officials certified the facility—where the fires, then twin blasts, originated—in 2014 for the storage of dangerous and toxic chemicals including butanone, an explosive industrial solvent, sodium cyanide and compressed natural gas.
A volunteer helping families evacuate from homes near the blast site said he had smelled the characteristic odor of bitter almonds linked with sodium cyanide.
"You can smell that smell within a radius of two or three kilometers (one or two miles)," the volunteer said. "We are providing the injured and their relatives with free face masks."
"Those on the front line [near the blast site] have been provided with chemical body suits and helmets," he said.
A report from state broadcaster CCTV said: "At present there is no water supply. Pungent smells fill the air."
"Citizens are worried that dangerous materials may pollute the air and they are prepared to evacuate from the area," it said.
Wednesday night's blast came after firefighters were called to a container wharf owned by Ruihai Logistics that was storing ammonium nitrate, potassium nitrate and calcium carbide at the time, after several containers had caught fire, police statements and official media reported.
Experts have speculated that the blasts may have been triggered when water was hosed on calcium carbide by firefighters.
The death toll was reported at 56 on Friday, and reports compiled by RFA suggest that at least 1,200 people were were injured.
The official Xinhua news agency said 721 people had been hospitalized, 25 of whom were in critical condition, however.
A team of 217 nuclear and biochemical materials specialists from the Chinese military are currently in Tianjin to inspect the site, it added.
Greenpeace warned on Thursday that rain could transfer airborne chemicals into water systems, and called for close and careful monitoring to identify what substances were being released into the air.
Government officials have yet to confirm what substances are involved.
Meanwhile, China's cyberspace administration has clamped down on media reporting of the disaster, ordering all domestic news outlets to use officially approved copy from Xinhua and "authoritative departments and media," according to a leaked directive published and translated by the U.S.-based China Digital Times (CDT) website.
"Websites cannot privately gather information on the accident, and when publishing news cannot add individual interpretation without authorization. Do not make live broadcasts." the directive said.
Meanwhile, the Tianjin propaganda department put out a directive banning editors, reporters for city TV stations, radio stations, newspapers, and new media or TV anchors from posting to social media about the blasts, CDT said.
A Chinese journalist in Tianjin, who declined to be named, said access to the blast site was getting more difficult, with security checkpoints on major highways.
"They allowed journalists to get closer to the area yesterday, but today we're not allowed," the reporter said. "They have set up police cordons on the major roads, for various reasons, including safety."
China's Internet censors were also out in force, deleting posts about the Tianjin disaster, netizens told RFA.
"I retweeted a couple of items that were critical about the blast, but they were all deleted," a netizen who declined to be named said. "Of course, I expected it."
Meanwhile, the editor of a local news site confirmed he had received warnings from China's Internet police to "be careful" about items from Tianjin. But he declined to comment further.
Online free speech activist Xiucai Jianghu said that any account of the Tianjin blasts that didn't accord with official statements would be treated as "rumor-mongering."
"They will take legal measures against this, not based on the facts, but based on what they ordered to be published," he said.
"The police think the Internet is territory they have to hold, but this obsession with toeing the party line is pretty old-fashioned," he said.
Sichuan rights activist Huang Qi, who founded the Tianwang rights website, said it is very difficult for any journalist to approach the blast site now.
"But the crucial thing is that they are deleting all of the photos and videos posted by netizens from the scene," Huang said.
"That's the thing we should really be concerned about."
Reported by Yang Fan for RFA's Mandarin Service, and by Huang Letao and Wen Yuqing for the Cantonese Service. Translated and written in English by Luisetta Mudie.