Chinese authorities have ordered the evacuation of residents within a 3km radius of the Tianjin blast site over fears of chemical contamination.
The evacuations came after an apparent change in wind direction, and as police confirmed the highly toxic chemical sodium cyanide was found near the site.
At least 112 people died in the blasts, officials said on Sunday, and more than 700 have been hospitalised.
Officials have identified 24 of the dead, with 88 still to be identified.
Remarkably, a man was found alive just 50m from the blast core, Chinese state news agency Xinhua reported.
The man was able to talk when he was found and is now in hospital, according to the report.
Latest pictures of the aftermath
People sheltering at a school used as a safe haven since the disaster have now been asked to leave wearing masks and long trousers, reports say.
The order came after a change in wind direction, prompting fears that toxic particles that would have been blown out to sea could be blown inland.
Troops equipped with chemical warfare protection have now entered the site of the blasts.
The People’s Daily newspaper tweeted that the specialist troops had been sent to handle the highly toxic sodium cyanide found at the site.
Police said the discovery occurred “roughly east of the blast site” in an industrial zone, according to state-run Beijing News.
The operators of the Tianjin site have been accused of violating safety rules.
The Chinese government has ordered officials to make nationwide checks on dangerous chemicals and explosives and to “crack down unwaveringly on illegal activities to ensure safety”