India, Feb. 2 -- Three wage labourers died inside an underground drainage line at the Kolkata Leather Complex on Sunday morning.

Kolkata mayor Firhad Hakim, who rushed to the spot, said that he has ordered a police inquiry into the incident.

It comes four days after the Supreme Court banned manual scavenging and manual sewer cleaning in the metro cities of Delhi, Mumbai, Kolkata, Chennai, Bengaluru and Hyderabad.

Hakim said: "One man fell ill after going down the manhole on a public road. The other two went down to rescue him. They all died because waste from the tanneries, which contains various chemicals, was flowing through the common drainage line. The waste is supposed to be sent to the effluent treatment plant. The local Bantala ...