High levels of sodium cyanide have been detected by wastewater monitors amid growing anger at the blasts which killed at least 114 people.

Alarming levels of sodium cyanide have been found at wastewater monitoring stations in the disaster-stricken city of Tianjin almost five days after a series of deadly explosions claimed at least 114 lives and sparked intense criticism of the Chinese government.

At a press conference on Monday morning, Bao Jingling, the chief engineer from Tianjin’s environmental protection bureau, said excessive levels of the toxic chemical had been detected in surface wastewater at the blast site. The highest levels detected were 27 times acceptable limits.

Prosecutors have been ordered to investigate possible dereliction of duty and abuse of power that may have contributed to Wednesday night’s blasts. “We must thoroughly investigate [the incident] and hold accountable all those responsible,” state media quoted Premier Li Keqiang as saying.

“We must give an answer for families of the victims, an answer for all residents of Tianjin, an answer for all Chinese people, and an answer for history.”

For days authorities have been scrambling to contain the fallout from the explosions that rocked Tianjin, a major port city around 75 miles east of Beijing, last Wednesday night, reducing an industrial estate on its outskirts into a debris-strewn wasteland.

About a hundred people whose residences were damaged in the disaster protested on Monday outside the Tianjin hotel where officials have held daily news conferences, calling for compensation from the government.

Displaced families and relatives of missing firefighters had already taken to the streets over the weekend to demand answers.

The explosions came after a fire broke out at a warehouse where as yet unknown quantities of hazardous chemicals including sodium cyanide are thought to have been stored.

Exposure to sodium cyanide – a white crystalline or granular powder with a variety of industrial uses – can be “rapidly fatal”, according to the US Centers for Disease Control and Prevention.

At least 70 people are still missing following the disaster, Gong Jiansheng, a Tianjin official, said on Monday. That number is thought to include many firefighters who tried to control the initial blaze and were caught up in the explosion.

There were reports over the weekend that 70 times the permitted quantity of sodium cyanide had been stored at the warehouse.

He Shushan, Tianjin’s deputy mayor, said “all sodium cyanide within 3km of the blast zone would “be collected and neutralised before Monday evening”.

During a visit to the disaster zone on Sunday, China’s prime minister, Li Keqiang, vowed to identify and punish those responsible for the calamity.

“We owe the families of victims, Tianjin people and all Chinese an answer,” he said, according to Xinhua, China’s official news agency.

Li ordered environmental officials “to keep monitoring the environment around the clock and release accurate, authoritative environment information as the public are highly concerned about the air, water and soil quality around the blast site,” according to Xinhua.

However, nearly five days after the disaster anger and frustration is rising. China’s state media has lashed out at the local government’s sluggish response to the disaster and its lack of transparency.

“During the first dozens of hours after the blasts, there was scant information offered by Tianjin authorities,” the Global Times complained on Monday in an editorial criticising their ‘fumbling’ response.

“Tianjin is not an exceptional case in terms of the inadequate disaster response work,” added the newspaper, which is controlled by Beijing.

The China Daily warned that a lack of concrete information about the situation in Tianjin had spawned multiple conspiracy theories.

“These conspiracy theories will build up a head of steam unless the government unravels the mysteries surrounding the incident with a thorough and transparent probe that is able to answer people’s questions,” it said.

There has been particular anger over how the government allowed a warehouse storing hazardous chemicals to operate so close to residential communities where thousands of people lived.

“Nobody told us that there were chemicals, or I would never have chosen to live here,” Liu Xuerui, a 27-year-old local whose home was damaged told the China Daily.