Three workers died after inhaling poisonous gas while working inside a septic tank at Sataish area under Tongi in Gazipur on Monday.
The deceased are yet to be identified.
Tongi Fire Service Station Officer Ashikur Rahman has confirmed the news.
Locals and eyewitnesses said the three workers entered inside the septic tank at a house in the area to repair it and fell unconscious inside the tank around 12pm.
Later, the house owner informed the fire fighters about the matter while the workers were rescued with the help of locals in critical condition and sent them to a nearby International Medical College Hospital where the doctors declared them dead.