Thousands of dead fish have washed up on the banks of the Haihe river about six kilometres from the site of the explosions at a chemical warehouse in Tianjin, stoking public fears over a leak of toxic chemicals.

Tianjin explosion dead fish cyanide
Thousands of dead fish are seen on the banks of Haihe River about six kilometres from the site of the chemical warehouse blastsReuters
Tianjin explosion dead fish cyanide
Dead fish float along the shore of Haihe River ChinaFotoPress via Getty Images

Officials said the dead fish were caused by regular seasonal low oxygen levels in the water and were not related to the blasts. Bian Shaowei, inspector with Tianjin Environmental Monitor Centre, said no cyanide was found in the water where the dead fish were spotted.

In an effort to test if the air inside the blast zone is safe, authorities took the unusual step of placing live animals in cages near the site of the explosions. According to local media, these guinea pigs (actually rabbits, pigeons and chickens) were still alive after two hours.

Tianjin explosion dead fish cyanide
A soldier wearing breathing apparatus runs behind cages containing pigeons, chickens and rabbits, which were placed near the site of last week's blasts at Binhai new district in TianjinReuters
Tianjin explosion dead fish cyanide
Rabbits are seen in a cage, which was placed near the site of the blasts. According to local media, the animals were still alive two hours laterReuters

, high levels of toxic chemicals have been found inside the core area, more than a week after the massive explosions that left 179 people dead or missing. Technicians have detected levels of cyanide as much as 356 times the national safe level within the evacuated area, although levels outside the zone show no undue contamination, according to state media reports. Workers in protective suits have started clearing wreckage, including charred car frames and crumpled shipping containers, from the site.

Tianjin explosion dead fish cyanide
People's Liberation Army (PLA) soldiers of the anti-chemical warfare corps are seen in protection suits at the site of the blasts in TianjinReuters
Tianjin explosion dead fish cyanide
Rescue workers remove water polluted by chemicals from the site of the explosionsReuters
Tianjin explosion dead fish cyanide
Rescuers wearing protective gear comb through twisted wreckage at the site of the blastsChinaFotoPress/Getty Images

The explosions created a hole measuring 100m wide and six metres deep. The crater is filled with an estimated 50,000 tons of water that is contaminated with cyanide. Equipment and pipes are being used to transfer the water to sewage treatment plants at a rate of 5,000 tons per day. The whole process could take two to three months.

Tianjin explosion dead fish cyanide
An aerial picture of the site of explosions at a large industrial area in the world's 10th busiest portReuters

Four new fires have broken out at the site. The official Xinhua news agency said one of the "combustion points" was in a logistics site for automobiles near last week's blast. The other three were within the central blast area, it said, without giving any explanation of the cause of the fires.

Tianjin explosion dead fish cyanide
Smoke rises from an area inside the exclusion zoneAFP

State authorities have confirmed that more than 700 tonnes of the deadly chemical sodium cyanide were stored at the Tianjin warehouse that blew up.

Tianjin explosion dead fish cyanide
Soil samples taken from an area near the explosions are placed on a table at a monitoring station to check for environmental pollutionKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
A paramilitary policeman wearing a mask stands guard within the 3km exclusion zoneKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
A drone operated by paramilitary police flies over the site of the explosions at Binhai new district in TianjinKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
Paramilitary policemen wearing masks operate a drone near the site of the explosionsKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
A digger and burnt-out cars are reflected in a pool of contaminated waterAFP
Tianjin explosion dead fish cyanide
Rescuers build a temporary barrier at the site of the explosions in an effort to contain vast amounts of toxic cyanideAFP

Executives of Tianjin Dongjiang Port Ruihai International Logistics, the company whose chemical warehouse exploded, used their connections to obtain fire safety and environmental approvals, according to the official Xinhua state news agency. "When we needed a fire inspection, I went to meet officials at the Tianjin port fire squad," said Dong Shexuan, 34, deputy head of the company. "I gave them ... the files and soon they gave me the appraisal and took care of it." Xinhua said Dong did not mention any instances of bribery.

Dong said company officials shopped around for approvals with different safety evaluation firms until they got the result they desired. The first such firm said the warehouse was too close to apartment buildings, he said.

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Satellite photos show the site before and after the explosions (Google/Skybox Imaging)

Public anger against the government has surged in the north-eastern port of Tianjin among residents of apartments near the blasts who believed authorities neglected to properly police the firm.

Tianjin explosion dead fish cyanide
An injured resident who was evacuated from his home takes part in a rally outside the venue of a government officials' news conference in TianjinKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
A woman carrying a baby both wear masks on a street in Binhai new district, around 5km away from the site of the explosionsKim Kyung-Hoon/Reuters
Tianjin explosion dead fish cyanide
People injured in the explosions at the chemical warehouse protest outside the hotel where authorities were holding a press conferenceAFP

Apartment buildings and a railway station were closer to the warehouse than allowed by Chinese regulations dealing with the storage of dangerous materials, state media has reported. Hundreds of people who lived near the blast site have demanded that the government arrange compensation or buy back their damaged or destroyed property.