Tianjin, China: Residents around the site of giant chemical explosions in the Chinese port of Tianjin were evacuated Saturday over fears of highly-poisonous sodium cyanide, state media said, as fresh blasts were heard and the death toll rose to 85.

A days-long fire intensified at the hazardous goods storage facility and the series of new explosions sent a thick black column of smoke into the air, the official Xinhua news agency said.

The decision to relocate anyone within three kilometres (1.9 miles) of the site came three days after gigantic explosions sent a huge fireball soaring into the sky and left a vast swathe of destruction.

It also came despite official assurances that the disaster had not released dangerous levels of toxic substances into the environment.

‘Residents in a relocation site of the blasts have been evacuated in fear of chemical pollutants in the air,’ Xinhua said.

Armed police were carrying out the evacuation after sodium cyanide was found at the site, the Beijing News said.

At a barrier on the edge of the evacuation zone masks were distributed to emergency personnel and police turned back anyone else, as at least 20 fire engines streamed in.

The area itself was already largely deserted, many of the buildings within it ruined, and an acrid smell hung in the air.

One couple carrying suitcases confirmed from behind their masks only that they lived within it, before leaving.

Officials said earlier that specialists from sodium cyanide producers were being sent in to the devastated industrial area where the blasts occurred.

Reports have said there could have been as much as 700 tonnes of the substance -- exposure to which can be fatal -- at the site. 

Soldiers trained in anti-chemical warfare techniques were also deployed.

Authorities have struggled to identify the substances present at the scene, sparking fears and scepticism among residents of Tianjin, which has a population of 15 million.