Three manual scavengers died of asphyxiation on Monday in Tamil Nadu’s Cuddalore district in an underground sewage tank, reported The New Indian Express. The incident comes days after three workers died while carrying out repair works at a mantle in Bengaluru.

The workers were appointed by the Tamil Nadu Water Supply and Drainage Board to clean the blockage in the underground sewage tank. Toxic gases inside the drainage tank killed the workers, identified as Jayakumar, Velu and Murugan.

Velu was the first to enter the sewage tank, but when he did not return, Jayakumar, who was the supervisor, sent Murugan to check on him. When there was no response from both of them, Jayakumar himself entered the tank. The fire department was called in by the passersby, who took the three to the hospital. They were declared dead by the doctors.

“I cannot say if someone was there to supervise the work as the case is under investigation. But there should have been engineers who supervised the work,” Vijaykumar, superintendent of police, told The News Minute.

Municipal officials said they have been insisting the water supply board ensure appropriate safety for the workers cleaning choked drains. “We have made arrangements for a motorised sewage suction truck to prevent workers getting into the manholes to clear any blockages,” an unidentified municipal official told The Times of India. The workers have demanded Rs 30 lakh as compensation to each of the families of the deceased and action against the contractor, The Hindu reported.