Six workers and one firefighter died Monday from sewage poisoning in an apartment compound in Beijing, local police said.

Three workers went down a sewage well to repair a sewage pump at 2:30 p.m. in Tongzhou District, east Beijing, but they were poisoned.

Another seven workers sent rescue them were also poisoned.

Firefighters then arrived at the scene and managed to rescue four workers. The other six workers died.

One firefighter also died after being poisoned as his gas mask was pulled off by a trapped worker.

The deaths are under investigation.

Source: Xinhua