Eleven people, including three children, died allegedly after inhaling toxic gas in the city's thickly populated Giaspura locality on Sunday, with high levels Hydrogen Sulphide detected in the air and authorities suspecting it was emanating from a sewer.
Four more persons, who were taken ill, are undergoing treatment at a hospital, officials said, adding the area was sealed, the residents were evacuated and a National Disaster Response Force (NDRF) team was at the spot following the incident.
A magisterial inquiry has been ordered into the incident while the Ludhiana Police has registered an FIR against unknown persons.
In the air quality sensors used by the NDRF team, high levels of Hydrogen Sulphide gas have been detected and this gas might have led to the tragic incident, according to an official release issued by the district administration.
The officials said they suspect that the poisonous gas was released after some chemical was disposed of in the sewerage in the area.
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.
The incident came to light on Sunday morning when some people who came to a local grocery store to buy milk started fainting. Four persons died on the spot while others were rushed to the hospital.
Among the dead were three members of the family that owned the store and five from another.
Police said five females and six males were among the dead.
The district administration announced Rs 2 lakh compensation each for the family of the deceased and Rs 50,000 each for those who were taken ill in the incident.
Union Home Minister Amit Shah expressed grief at the loss of lives and said the NDRF team is engaged in relief work.
Punjab Chief Minister Bhagwant Mann said the incident was very painful and added that all possible help is being provided. Health Minister Balbir Singh visited Ludhiana and took stock of the situation in the area and at the civil hospital.
The minister said exemplary action would be taken against perpetrators of this tragedy.
Ludhiana Deputy Commissioner (DC) Surabhi Malik had earlier told reporters, "It is likely that there was some gas contamination. We are collecting samples from manholes."
As the smell of the gas started spreading, many people moved out of the area.
The DC said the cordon at the scene of the leak will be extended. She said those who died in the incident did not show any symptoms of respiratory problems.
"It is likely that because of neurotoxins the deaths took place," Malik added.
Additional Deputy Commissioner Amarjit Singh Bains said, "A broken manhole has been found in the area and there was a strong smell emanating from it. There is a possibility that the chemical has been poured into the sewerage from that point".
Malik said there was no need to panic and asked people not to fall prey to any rumour-mongering.
She also appealed to people to stay away from the area. "A check will be conducted to see how far this gas has spread," the DC said.
She further said that CCTV cameras were being scanned.
The DC said different teams of district administration, police, municipal corporation and Punjab Pollution Control Board are stationed at the site.
Ludhiana Police Commissioner Mandeep Singh Sidhu said it is suspected that someone disposed of some chemicals in the sewerage which led to the emission of the toxic gas.
"A cat was also found dead at the incident site," said Sidhu.
Through the public address system, people were asked to stay away from the area, said Sidhu.
Police also deployed drones to check for other victims who could be lying unconscious.
The deceased were identified as Kamlesh (60), Varsha (35), Aryan (10), Sourav (35), Preety (31), Kavilash (40), Kalpna (16), Abhay (13), Navneet (39), Neetu Devi (39) and an unidentified person. "
"The incident of gas leak in Giaspura area of Ludhiana is very painful. Teams of police, district administration and NDRF are present on the spot. Every possible help is being provided...," Chief Minister Mann said in a tweet in Punjabi.