Three labourers were missing after falling deep inside a drain while clearing the manhole at the Kolkata Leather complex on Sunday, police said.
A police officer said one labourer tripped and fell over 20 feet down while clearing the manhole clogged with effluents of the leather units at the Kolkata Leather complex in the Bantala area.
Two others behind him also fell inside. Personnel of the disaster management force and fire brigade were trying to rescue them, he said.
The three were identified as Farzan Sheikh, Hasi Sheikh and Suman Sardar.
It was not known whether the three were wearing masks to work under manhole cover.
A Kolkata Municipal Corporation official said the three labourers were not part of the corporation's team.
"They must be part of the team of the industrial unit management," he said.
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