Officials of Tanggu Bureau of Aquatic Products investigates the cause of dead fish

Tianjin Environmental Monitoring Center has launched an investigation into the cause of death of thousands of dead fish washed ashore in the port city of Tianjin, according to Director Deng Xiaowen.

 Deng said they have involved experts from the local fishing and aquatic departments to find out the reason and will announce to the society immediately.

Earlier he told a press conference that no toxic levels of cyanide have been detected in water samples takenfrom a Tianjin river where a large number of dead fish were spotted after last week' s explosions in the port city.

He said in hot summers, it is normal to see large quantities of dead fish offshore, because the pollution on the land may flow into the river and sea after rainfall, which may cause eutrophication and suffocate the fish.

Several pictures showing large quantities of dead fish in the offshore area of Tianjin have gone viral online since Wednesday . Some residents are concerned that hazardous chemicals from the blast have contaminated the sea.