The men had been hired by a private contractor to clean the tank of an apartment in Kundli area, they said.
"They inhaled a poisonous gas while cleaning the water tank," a police officer from the Kundli Police Station said.
Meanwhile, the victims' families have alleged negligence on part of the contractor and delay in providing emergency rescue services.
They also tried to block the GT Road by placing the bodies on the highway. However, the police foiled their attempt to do so.
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