With the public anxious that their air may have become hazardous to breathe, local authorities in Tianjin say they have not yet been able to determine what chemicals ignited in this week’s massive warehouse explosion. Deputy director of Tianjin’s work safety supervisory board Gao Huaiyou said they have been unable to identify the chemicals due to major discrepancies between company records and customs records.

However, another report says workers are now trying to remove 700 tons of sodium cyanide that did not get destroyed in the massive explosion. People’s Daily says sodium cyanide was only found on the premises, but would not confirm it was one of the chemicals that caught fire on Wednesday night.

According to the Beijing News, sodium cyanide has now been detected in the sewage runoff, while Tianjin firefighters have said potassium nitrate and sodium cyanide were contained in the warehouse that was destroyed by the explosion.

There are fears that dangerous gases are spreading to Beijing, but a south-westerly wind has pushed many contaminates in the opposite direction to the Bohai Sea. But while air might be safe, water from two drainage sites have been shown to contain hazardous materials. Levels of the chemical Oxygen Demand (COD) and cyanide were found in Tianjin water to be three and eight times higher than the allowable safety standard, respectively, by the Ministry of Environmental Protection.

The Tianjin blast is responsible for killing 50 people and hospitalizing another 701.