Rescue crews get disinfected after cleaning up the blast zone in Tianjin, August 19, 2015. [Photo/Xinhua]

Given the vast variety of dangerous chemicals and their complicated placement, no deadline for the cleanup could be given, He Shushan, vice-mayor of Tianjin in charge of work safety, said on Tuesday.

Authorities have been ordered to monitor air, soil and water quality near the site around the clock. Emergency response plans should be made to prevent major accidents that cause pollution, the statement said.

Armed police and public security officers as well as firefighters have made great sacrifices in responding to the incident, the statement said.

Whoever is responsible for the accident will face punishment in accordance with the law, it said, adding that penalties will be meted out to those found guilty of dereliction of duty and breaking the law.

Dead fish

Photos taken on Thursday showing large quantities of dead fish about 4 kilometers from the blast site immediately went viral.

In response, the Tianjin Environment Monitoring Center sampled the water on Thursday evening and found no cyanide, the center reported on its website.

It is not the first time this summer that a large amount of dead fish has been found in Tianjin, and the authority will give more detailed information about this incident as soon as it is available, said Deng Xiaowen, head of the center.

Xinhua contributed to this story.