Police identified the deceased as Dileep and Pintoo (both from West Bengal) and Murugesan and said the incident happened in the wee hours of Saturday.
When Dileep's footwear slipped and fell into one of the structures he tried to retrieve it and was asphyxiated. When Pintoo tried to survey the fate of his colleague, he met with a similar fate, police said.
When a supervisor summoned Murugesan to know the fate of the two persons, he went down the structure and also died of asphyxiation, police said adding the bodies were later retrieved by personnel of Fire and Rescue Services.