Three people died and another person fell sick after inhaling toxic gas in a septic tank of an under-construction building in Bank Colony area of Nasrsingdi on Monday.
The deceased were identified as Sirajul Islam, 32, sub-contractor of the building project hailing from of Chandpur district, and workers Ramij Uddin, 26, and Rakib Miah, 22, of Shibpur upazila in Narsingdi.
Officer-in-charge of Narsingdi Model Police Station Syeduzzaman said two workers climbed down the septic tank to complete the last-stage work on it.
According to UNB, getting no response from them, Sirajul also got down only to go silent.
Worker Jamal fell sick as he peeped into the septic.
The trio was later rescued and taken to Sadar Hospital where doctors declared them dead.