Four sanitation workers died of suspected asphyxiation in the early hours on Monday at Bardu village, in Madhya Pradesh, police said.
Vijay Sihote (20), Ishwar Sihote (35), Dinesh Goyal (35) and Rinku Goyal (16) died while cleaning a septic tank, Inspector B L Meena of the Pipalrava police station said.
He said one Kamal Singh Sendhav had hired them to empty the tank for Rs 8,000.
The bodies have been sent for postmortem, Meena said adding the exact cause of their death would be known once the autopsy report is received.
It appears that they died of asphyxiation. However, the possibility of them inhaling some poisonous gas cannot be ruled out, he said.
Earlier this month, four sanitation workers had died of asphyxiation while cleaning a tank in Ghitorni in the national capital.
According to a report by The Hindu, around 250 sanitation workers in the capital get inside storm water drains and sewer lines to clean them. Most of the workers work without wearing any safety gear, the report added.
(With PTI inputs)