The Punjab Police on Monday formed a five-member Special Investigation Team to probe a gas leak in Ludhiana’s Giaspura area, PTI reported.

Eleven people, including five from one family and three from another, had died after inhaling toxic gas in the industrial area on Sunday. The gas is suspected to be hydrogen sulphide, which was allegedly disposed of in the sewage and emanated from a broken manhole. Officials are still trying to identify the source of the leak.

On Monday, Ludhiana Police Commissioner Mandeep Singh Sidhu said that the Special Investigation Team will be led by Deputy Commissioner of Police (Investigation) Harmeet Singh Hundal. The team will investigate if any industrial unit dumped its waste in the sewerage line.

Sidhu sought the cooperation of the Punjab Pollution Control Board in the case and warned that action would be taken against it if its officials do not cooperate, according to The Indian Express.

“PPCB [Punjab Pollution Control Board] is the nodal agency to check pollution and the working of industries,” Sidhu said. “It is their job to check if industries are involved in any wrongdoing. It is only PPCB officials who can tell us which industries were complying with norms and which were not. What if some industry was dumping waste into sewage through an internal connection?”

Sidhu added that the initial investigation suggests that an electroplating factory might have dumped waste in the sewage. “And it was not done just for a day, it was being done continuously and the build-up finally led to this tragedy,” he said.

Punjab Pollution Control Board Member Secretary GS Majithia said that an inquiry is underway by his own team.

“Hydrogen sulphide is a sewer gas,” he said, according to The Indian Express. “We are conducting a probe. Teams are on the ground to collect samples and check industries within a 200-metre radius. The report will be compiled within two days to check if any industry discharged effluents in sewage.”

Meanwhile, district authorities said that a decontamination drive, which involved putting caustic soda in drains and sewerage lines to counter the hydrogen sulphide build-up, was done.

“Hydrogen sulphide was no longer detected in the air,” Ludhiana Deputy Commissioner Surabhi Malik said. “During the night, the level of hydrogen sulphide in the manholes was high but it went down after the chemical decontamination process. Why was so much build-up [of gas] in this area only is a matter of investigation.”