Six persons, four of them members of the same family, died of suffocation after inhaling poisonous gases when they entered a septic tank in East Champaran district, police said.
The incident took place at the house of Dinesh Mahto, 45, in Bela Jeepur village under Jitna police station area, Deputy Superintendent of Police Alok Kumar Singh said.
He said Dinesh entered the septic tank to clean it and the five others also went inside it to rescue him after realizing that he had fallen unconscious.
They also died after inhaling poisonous gases in the tank, the DSP said.
The other five were his wife Bachani Devi, sons Mohan Mahto and Basant Kumar, besides neighbours Sachin Mahto and Saroj Mukhiya, the deputy SP said.
The bodies have been sent for post-mortem.