Three labourers died of suffocation while cleaning the sewage treatment plant (STP) of a housing complex here shortly after midnight Friday, civic officials said.
A total of eight labourers were involved in the STP cleaning operation in the complex in Kapurbawdi when they got stuck inside the plant, said Santosh Kadam, chief of the Regional Disaster Management Cell of the Thane Municipal Corporation (TMC).
Five of them were rescued by fire brigade personnel, while the remaining three choked to death at around 12.30 am, he said.
Kadam said the deceased were identified as Amit Puhal, 20, Aman Badal, 21 and Ajay Bumbak, 24.
The rescued workers were admitted to a government hospital for treatment, he said.
The Kapurbawdi police have registered a case of accidental death and sent the bodies for a postmortem, civic officials said.