A portion of the Giaspura locality in Punjab's Ludhiana where 11 people died allegedly after inhaling toxic gas remained cordoned off on May 1 while the district authorities said the affected area underwent a night-long decontamination process.
Teams of the Punjab Pollution Control Board checked what led to the buildup of Hydrogen sulphide in the sewer that might have led to the tragedy, the officials said, adding that the poisonous gas is no longer being detected in the air.
Eleven people, including three children, died after allegedly inhaling toxic gas in the city's thickly populated Giaspura locality on Sunday, with high levels of Hydrogen sulphide detected in the air and authorities suspecting that it emanated from a sewer.
Four more people who were taken ill are undergoing treatment at a hospital.
A magisterial inquiry has already been ordered into the incident and the police have registered an FIR against unknown persons.
Giaspura is a thickly populated area with a migrant population. Several industrial and residential buildings are located there. All the victims belonged to Uttar Pradesh and Bihar and had been staying in Ludhiana — Punjab's industrial hub.
Ludhiana Deputy Commissioner Surabhi Malik on May 1 said the area was successfully decontaminated.
"The whole (Sunday) night, teams of the National Disaster Response Force and the municipal corporation took readings of ambient air quality in the area and Hydrogen sulphide was not detected in the air," Ms. Malik told PTI.
The teams also checked the manholes in the area at frequent intervals.
"During the night, the level of Hydrogen sulphide in manholes was high but it has declined to a lower level after chemical decontamination," she further said.
Ms. Malik said the Punjab Pollution Control Board teams are checking what led to the buildup of Hydrogen sulphide in the sewer.
Hydrogen sulphide, also called sewer gas, is a poisonous gas that smells of rotten eggs and can lead to fast unconsciousness and death.
The officials had suspected that the poisonous gas was released after some chemical was disposed of in the sewerage in the area.
A pollution control board team is mapping industries located in the area to check the inlet and outlet of their water, the Ludhiana Deputy Commissioner said.
The authorities are also checking CCTV camera footage to see if anybody had disposed of any chemicals in the sewer.
Ms. Malik said, "The cordons will be reduced carefully." The authorities had cordoned off around 600 metres of the area.
The police have registered an FIR under Section 304 (culpable homicide not amounting to murder) of the Indian Penal Code against unidentified persons.
The incident came to light on April 30 morning when some people who came to a local grocery store to buy milk started fainting. Four persons died on the spot while the others were rushed to the hospital.
Among the dead were three members of the family that owned the store and five from another. Five women and six men were among the dead.
