TIANJIN, Aug. 13 (Xinhua) -- Toxic fumes detected in the air after blasts ripped through the Tianjin Binhai New Area are within national standards, Wen Wurui, head of the city's environmental bureau said.

At 4 p.m., police detected high densities of toxic gases, including sulfur dioxide, carbon monoxide and nitrogen oxides, within 500 meters of the fire, but they were not detected 2 km from the fire, the headquarters said.

The city began to monitor air and water quality immediately after the blast, setting up 17 monitoring stations for air and five for water.

Discharge into the sea has been closed as the water is tested, Wen added.

At 4 a.m. Thursday, less than 2 milligrams per cubic meter of epoxyethane, a carcenogenic gas, was found in the most polluted area. It is considered hazardous at 5 milligram per cubic meter.

At 5:30 a.m., the concentration of methylbenzene and volatile organic compounds, both harmful gases, slightly exceeded safety standards.

As of 11 a.m., all toxic gas indicators were within their normal range.

Specialized anti-chemical warfare troops are on site.