Three workers died of asphyxiation after inhaling poisonous gas while repairing a sewage pumping station in Madurai on Thursday night, The Hindu reported.

The three victims have been identified as Sivakumar, Lakshmanan and Saravanan. They were contractually employed by the Madurai Corporation.

“We believe that Sivakumar, 40, who first got into the sewage tank, which has a depth of around 30 feet, to fix the motor fell unconscious after he inhaled the poisonous gas at around 9 pm,” Madurai Deputy Mayor T Nagarajan told The Hindu.

The other two workers subsequently fell into the tank after inhaling the poisonous gas.

“One of them couldn’t even be retrieved,” said a relative of one of the deceased workers to the Hindustan Times. Two workers were taken to the hospital in a two-wheeler since there was no ambulance. However, they could not be saved, the relative said.

“They have died due to government negligence,” he said. “We have lost three lives only because they didn’t use machines.”

The police dismissed allegations of negligence and said that fire department and rescue officials had immediately reached the spot.

A fourth person, Karthik, who was involved in the rescue operation, was sent for treatment to the Government Rajaji Hospital after he showed signs of inhaling the poisonous gas as well, the India Today reported.