Seven workers were killed and two injured after exposure to poisonous gasses at a paper mill in central China, authorities said Saturday, in the latest in a spate of deadly accidents to strike the country involving dangerous chemicals.

The accident occurred Friday after an employee fell into a pool filled with poisonous waste paper pulp during a cleaning operation, a statement from the Anxiang county government in Hunan province said. His co-workers rushed to help him but were overcome by the noxious gasses, the statement said.

It follows China's worst industrial accident in recent history, a massive explosion at a warehouse storing toxic chemicals in the port of Tianjin that killed at least 145.

Police have arrested 11 local officials and company executives in that incident along with a dozen employees of the firm involved. Nationwide safety checks were ordered after the Aug. 12 disaster, focusing especially on the storage of dangerous chemicals.

All the government officials are accused of dereliction of duty and abusing their positions, pointing to major gaps in China's regulation of industrial safety and management of toxic substances.

Investigators are looking into how the Tianjin warehouse gained permission to handle sodium cyanide and other dangerous chemicals despite being located inside a legally-mandated 1,000-meter (1,000-yard) buffer zone from homes and roads. The investigation has also found that the warehouse was storing vastly more chemicals than it was equipped to handle and had kept some in a loading zone rather than storing them securely.

Another worker was killed and nine injured in an explosion at a chemical plant in the eastern city of Zibo on Aug. 22.