Shenzhen Vice Mayor Lu Ruifeng, hundreds of officials and experts from the district and municipal officials participated in the city's first chemical leak drill since March, which was held in Bao'an District on Thursday.

"Chemical plants and other industrial manufactories dot the crowded Bao'an and Longgang districts," said a spokesman for the municipal environmental protection bureau surnamed Luo. "As a slight leak of toxicant can affect many, we therefore conduct such a drill to test our capability in dealing with emergent leakage."

During Thursday's drill, a tanker with five tons of industrial solvent containing benzene and toluene leaked some of the chemical during unloading at the Xijiang Chemical Plant in Bao'an.

Benzene and toluene are colorless and flammable aromatic hydrocarbons. Breathing high levels of benzene or toluene can result in death, while low levels can cause headaches, unconsciousness and chronic damage to the bone marrow.

The plant immediately turned off the vehicle's safety valve, evacuated all staff and reported to the district environmental protection bureau.

The district bureau called the city government after realizing the contaminants had diffused into the air and nearby water sources.

The municipal environmental protection bureau cleaned up the chemical on the ground and in the sewage pipes and monitored the air pollution level every five minutes.

The drill lasted for about one hour.

Editor: Donald