At least 10 people have died in similar incidents in the national capital region over the last two months.
SP (City) Arun Kumar Singh said the three men got stuck in the narrow sewer line yesterday and choked to death on toxic gases.
They have been identified as Rajesh, Vikas and Ravinder. Their bodies were taken out late last night.
The Noida Authority, which had awarded the contract to Lal, today announced a compensation of Rs 10 lakh each to the families of the deceased.
The police said an FIR will be registered against the contractor if a complaint is filed in this regard.
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