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, Mr 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.