The bodies of two children were recovered from the uncovered septic tank in Sat Mandir Road area of West Chhagalnaiya municipality in Feni late Friday night.
The deceased were identified as Faisal Farabi, 9, son of Qatar expatriate Iqbal Hossain of East Shilua village in Pathannagar union and Sakhawat Hossain, 8, son of Dubai expatriate Shamsul Haque of Durgapur village in Ghupal union.
The children went out to play and might have entered a nearby under-construction building where they accidentally fell into the open septic tank on the premises, said Chhagalnaiya Police Station Sub-Inspector Salauddin Rashed.
Later, with assistance from the Fire Service and Civil Defence, their bodies were recovered from the tank.
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Locals said the building was still under construction and lacked basic safety measures.
The mouth of the septic tank was left uncovered with no warning signs or protective barriers in place.
The tragic deaths cast a pall of grief over the area.
Police said the bodies were recovered and further legal steps will be taken in consultation with the families.