Three labourers died while cleaning a septic tank in Nalasopara town in Palghar district in Maharashtra on Friday. The incident took place in Anand View Apartments in Nilemore locality, the police said according to PTI.

“The three labourers, who were in the age group of 25 to 35, went into the septic tank to clean it,” Palghar police spokesperson Hemant Katkar said. “However, they died inside possibly due to inhalation of toxic gases.”

A supervisor had hired six workers to clean the tank, The Times of India reported. One of the workes died after entering the tank and inhaling toxic gases. Two others, who entered the tank to rescue him, also died. The three labourers were identified as Sunil Chavriya, 30, Pradeep Sarvay, 25, and Bika Bumbak, 25.

Personnel from the fire brigade and a team of the disaster management cell pulled out the labourers’ bodies from the tank. The bodies have been sent for autopsy, the police officer added.

“Eight persons have been booked on charges of negligence,” Katkar said. The supervisor has been detained for questioning.