On August 12, huge explosions at a chemical storage facility in Tianjin, in northern China, killing at least 112 people and injuring at least 700. They also made people worry about being poisoned by some of the chemicals that may have been stored there, for example sodium cyanide.
Here's what we know so far:
How did the explosions happen?
Firefighters were called to a fire at a dangerous-chemicals storage facility on Wednesday night in Tianjin.
Then, two huge explosions took place about 11:30pm, sending a giant fireball sweeping across the area.
Authorities have struggled to find out what exactly caused the explosions, or what chemicals were stored at the facility.
But questions have been raised over whether the firefighters could have caused the explosions by spraying water over calcium carbide, listed as being at the site.
Calcium carbide reacts when wet to produce highly combustible acetylene gas.
How many people were killed or hurt, and who were they?
At least 21 of the 112 people confirmed killed were firefighters, many of whom who came to tackle the first fire, officials say. Others were migrant workers who lived in dormitories nearby.
Overall, 722 people have been admitted to hospital, 58 of whom were in critical or serious condition last night.
Most of the recovered bodies have yet to be identified and around 85 firefighters are still missing, officials said today.
Several police are also missing, but a police officer quoted in Chinese media on Saturday said his station's losses had not been included in the toll at that point.
Officials have said 17,000 families were affected by the blast, 1,700 factories and 675 businesses.
How bad is the damage?
Epic. Residents likened the shockwaves to an earthquake, and aerial video 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.
About 10,000 new imported cars near the blast site were destroyed and even buildings three kilometres away had their windows shattered.
Up to 6,000 people were relocated on Thursday to schools because their homes were damaged by the shockwaves,
What chemicals were at the storage facility?
Officials have a long list of chemicals that may have been at the dangerous goods storage facility when the explosions happened, but have been unable to say exactly which ones were there.
Potassium nitrate and ammonium nitrate are believed to have been there.
Chinese reports said 700 tonnes of sodium cyanide were at the site, and officials called in experts who make the deadly poison to help handle it. Hydrogen peroxide, which neutralises it, has been used.
A military team of 217 chemical and nuclear experts was sent in early on, and rescue teams wore protective clothing in the blast area.
What else could go wrong?
Extremely dangerous chemicals could be floating in the air, may still be leaking from the facility or could cause another explosion.
Chinese officials have given mixed signals about the threat level. They have said that even though there is more chemicals in the air than normal, the air is still safe to breathe. But, some police and others and been seen wearing gast masks and full protection suits at the scene.
On Saturday people were moved away from a three-kilometre radius from the site of the blasts, state-run media reported. Officials said later the reports were wrong, but barriers stopped people going into the zone and others were seen leaving.
Xinhua reported late Saturday that there had been 10.9 times more cyanide in waste water than there was on Thursday. It had since weakened but was still more than twice the normal limit, it said.
What is sodium cyanide?
Sodium cyanide is a white crystal or powder. It releases hydrogen cyanide gas, which the US Centers for Disease Control describes as a highly poisonous chemical that interferes with the body’s ability to use oxygen”.
The gas has a special smell of bitter almonds, it says, but many people cannot smell it. Sodium cyanide can kill people very quickly, it said.
The chemical has been used in the US to carry out executions in gas chambers.
Sodium cyanide is used in the mining industry to recover gold, among other industrial purposes.
How has the government responded?
Authorities have struggled to completely put out the fire, whichbecame stronger yesterday, when several fresh blasts were also heard.
The government has also blocked some criticial posts on social media and suspended or shut down more than 360 social media accounts "for spreading rumours about Tianjin".
Fifty 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.
Bosses from the company that ran the storage facility, Tianjin Dongjiang Port Rui Hai International Logistics, were quickly arrested on Thursday.
Firefighters, military and other rescue workers have continued to search for people still believed to be missing.