天津仓库化学品爆炸尚未查明

There are now 56 confirmed deaths, including 21 firemen, from the massive explosions and fire in the port city of Tianjin.

Of the 721 people who were injured during the incident on Wednesday, 25 remain in critical condition.

As of this evening, four sites are still on fire, but authorities say each situation is basically under control.

There was a small explosion at noon today.

More than 500 firefighters are still trying to put off the fires and the rescue operation is ongoing.

Rescuers found a survivor earlier this morning.

The 19-year-old firefighter, named Zhou Ti, is from the Binhai New Area brigade of Tianjin's fire department.

He is said to be in stable condition.

Meanwhile authorities are still trying to find out what is exactly inside the warehouse.

Designed to house dangerous and toxic chemicals, the warehouse was storing mainly ammonium nitrate, potassium nitrate and calcium carbide at the time of the blasts.

Gao Huaiyou, deputy director of Tianjin's work safety watchdog, says the company which owns the warehouse suffered severe damage and there are major discrepancies between the accounts of company management and customs records, which makes it difficult for them to identify the chemicals.

Authorities did find toxic chemicals at the explosion site, including cyanide stored in the area.

Hazardous substances have been detected from two drainage outlets near the blast site.

The concentration of Cyanide found in the water is said to be eight times higher than the national standards.

Liu Zuohong, an inspector from the environmental protection ministry, says they are now taking steps to process the contaminated water.

"First, we have to close this cofferdam, the isolating space between two adjacent steel bulkheads or decks, and then use the cement to fill it up. And we can see both these two water cubes have also been filled with cement."

In the meantime the municipal authorities of Tianjin also say that air pollutants monitored around the blast sites reduced to normal level yesterday.

For more on the pollution conditions caused by the blast, we spoke earlier with He Jingjing from the Institute of international environmental law of the Academy of Social Sciences.