Five workers died after they went down a waste water treatment tank of a food processing factory in Bang Na area this morning.
The waste water treatment system is in the compound of CPF Thailand Plc.
Rescuers and police said they were alerted of workers falling into the waste water tank and quickly rushed to the scene.
Five workers were pulled out of the tank but four were dead.
Another was rushed to hospital as he was still alive but in critical condition.
However the worker died later at hospital.
Police said they believed the workers suffocated first when they went down the tank to clean, and fell into the waste water.
They were examining the waste water treatment closely to find the exact cause and those responsible for the tragedy.
Source: Thai Public Broadcasting Service (Thai PBS)