Kolkata, Oct. 14 -- Four members of a family were killed after inhaling toxic gases inside a septic tank at their residence in Mohanpur in West Midnapore district of West Bengal on Tuesday afternoon, police said.

Police officers said that Badir Mallick, a 45-year-old mason, had constructed the septic tank at his sister's house a few months ago. Mallick fell into the tank on Tuesday afternoon after a wooden plank, which was being used as a cover, gave way.

Mallick's sister, Najera Bibi (38), who was standing nearby, climbed down to rescue him. Later, Najera's son, Sheikh Rabiul (25), and her nephew, Sheik Soyeb (27), also climbed down to help. None of them returned.

"All four bodies were recovered by the villagers in an unconscious stat...