The tragedy struck the densely populated area in Punjab's industrial hub on Sunday.
A five-member Punjab Police Special Investigation Team (SIT) was set up to investigate the Giaspura locality gas leak incident here in which 11 people died after allegedly inhaling toxic gas, officials said on Monday.
Besides, teams of the Punjab Pollution Control Board (PPCB) were also probing the cause behind the build-up of the hydrogen sulphide gas which was suspected to have led to the tragic incident, they said.
The tragedy struck the densely populated area in Punjab's industrial hub on Sunday.
District authorities said the locality underwent a night-long decontamination process, involving putting caustic soda in drains and sewerage lines to counter the hydrogen sulphide build-up. Traces of the gas are no longer present in the area, they added.
Hydrogen sulphide, also called sewer gas, is poisonous and smells like rotten eggs. It can lead to unconsciousness and death.
Speaking to the media, Ludhiana Police Commissioner Mandeep Singh Sidhu said the SIT will be led by Deputy Commissioner of Police (Investigation) Harmeet Singh Hundal.
Sidhu said the team would investigate if any industrial unit dumped waste in the sewerage line. He said police would seek cooperation of the Punjab Pollution Control Board in the case, and if its officials do not cooperate, action would be taken against them too.
A pollution control board team is mapping the industries located in the area to check the inlet and outlet of their water, said the officials.
Meanwhile, a Ludhiana-based industrial body feared "harassment" by the certain government departments for the gas leak tragedy.
"The industry implemented norms and guidelines issued by the different government departments to run factories and the reason behind this incident is something different," said Upkar Singh Ahuja, president of Chamber of Industrial and Commercial Undertakings (CICU) in a statement.
Ahuja said the government should conduct a root cause analysis of the incident.
"Industry is a soft target. Whenever any such incident occurs, industry is blamed for this," said Ahuja later in a video message.
Ahuja also asked industry members if they are harassed, they should contact the CICU.
He, however, said if anybody is found violating norms, action should be taken against him but they will not allow any innocent industrialist be harassed.
The district officials earlier said the poisonous gas might have been released after some chemical was disposed of in the sewerage in the area. The authorities are scouring through CCTV footage to confirm this.
"Hydrogen sulphide is generally found in sewer and it is called sewer gas. Why there was so much build-up (of gas) in this area only, it is a subject matter of investigation," Ludhiana Deputy Commissioner Surabhi Malik said, while adding when lab reports of PPCB comes, it will throw more light on the incident.
Meanwhile, an event dedicated to observing the International Labour Day near Sherpur Chowk on Monday was put off in the wake of the tragic incident, said Ludhiana South MLA, Rajinder Pal Kaur Chhina, in a statement.
Earlier, three members of a family who died in this incident were cremated here, amid heart-wrenching scenes.
A magisterial inquiry has already been ordered, and police have registered an FIR under IPC section 304 (culpable homicide not amounting to murder) against unidentified persons.
The incident took place on Sunday morning when some people, who had come to a grocery store in the Giaspura locality, fainted. Four died on the spot, while the others were rushed to a hospital.
All the 11 who died were from Uttar Pradesh and Bihar. Giaspura has a very high migrant population where several industrial and residential buildings are located.
Among the dead are three members of the family that owned the grocery store and five from another.
Sourav Goyal (35), his wife Preety (31) and his mother Kamlesh Goyal (60) were among 11 people who lost their lives in the incident.
The couple's eight-month-old son Yug had a miraculous escape in the incident. Sourav's brother Gaurav (50) lit the funeral pyres holding the baby in his arms.
The bodies of seven more victims, including five members of a family, have been sent to their native places in Bihar for the last rites.
Ludhiana Deputy Commissioner Malik said the area has been decontaminated. Teams of the National Disaster Response Force and the municipal corporation took readings of the ambient air quality in the area throughout the night, she told PTI, adding that hydrogen sulphide was no longer detected in the air.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)