China's leaders vow to severely punish officials responsible for Tianjin's deadly blasts

The central leadership has vowed to thoroughly investigate the deadly blasts that killed 114 people in Tianjin last week and to severely punish officials responsible for the tragedy.

A special session of the Communist Party Politburo Standing Committee, chaired by President Xi Jinping , was held to discuss the disaster on Thursday as officials admitted that cyanide levels in water close to the accident scene were 356 times higher than the national acceptable limit, and thousands of dead fish appeared in a river near the site.

A statement after the meeting said rescue efforts, environmental monitoring and clean-up of the explosion site should be stepped up and officials would be held accountable.

"Whoever is responsible for the accident will face punishment," it said.

Adding to fears that a toxic sodium cyanide spill at the blast site threatened public health, a sea of dead fish washed up on a section of the Hai River, about 6km from the scene of the accident. Local authorities said no cyanide was detected in the water in the area.

Deng Xiaowen, director of the Tianjin environmental monitoring centre, has promised to conduct tests to find out the cause of the fish deaths.

An enormous water pit created by the blasts - 100 metres wide and 6 metres deep - is also proving a big headache. The average concentration of cyanide found in water in the pit was 40 times higher than the safe limit, state-run CCTV reported.

Excessive levels of cyanide were detected in eight of 26 monitoring locations, with the highest at 356 times the national permitted limit, Deng said.

But he also noted that no cyanide pollution had been found outside the core explosion site, and that mass fish deaths often occurred after rain in summer.

Meanwhile, The Beijing News reported that Ruihai International Logistics - the company at the centre of the blasts - had been operating from as early as March last year, before it was licensed to do so from the Tianjin Municipal Transport Commission's port management bureau.

The firm was not equipped to store dangerous chemicals, but the bureau allowed it to do so on a trial basis from April to October 2014, the report said, citing a government document that marked the approval as "not for public review". The newspaper accused the bureau of violating regulations by granting Ruihai approval before the company was adequately prepared to do so. Ruihai obtained its safety review certification only in August last year.

After the company's temporary licence expired in October, Ruihai operated its business without official approval for eight months, before it received its licence in June.