
The incident took place at noon in the Volail Gedder Bazar area of Kashipur, at a newly built building owned by Shahabuddin, locals said.
The deceased were identified as Delwar Mridha (35), son of Altaf Mridha of Bhangra village under Bauphal upazila of Patuakhali, and Rana (22), son of Abdul Rahim of Palashbari upazila in Gaibandha.
Delwar was a mason by profession and father of a one-and-a-half-year-old son. Rana worked at a garment factory and had joined Delwar for construction work on his day off. He had been married only four months ago, according to family members.
Locals said the accident occurred while shuttering work was being removed from the water tank, when the workers were exposed to accumulated toxic gas inside the structure. They soon developed breathing difficulties and lost consciousness.
Fire service personnel rescued them from the spot and rushed them to Khanpur 300-bed Hospital, where doctors declared them dead on arrival.
Duty doctor Shahadat Hossain said both had died before reaching the hospital, adding that the preliminary cause of death was likely suffocation due to toxic gas inside the tank, reports UNB.