The discovery of the corpses took place in Charmadhua area of the upazila on Thursday morning
The four traders are Abdul Hakim and Farid Miah, of Abdullahpur village, Anwar Hossain, of Baherchar and Khalil Miah, of Mehernagar village. The four are residents of the upazila.
Upazila Nirbahi Officer Abdul Matin confirmed the matter to the Dhaka Tribune.
Locals informed police after tracing the bodies afloat in the area. Police handed over the bodies to the families.
The district administration gave Tk10,000 to the families each for funeral and 20kg rice while the upazila authorities gave them Tk5,000.
A cattle-laden engine-driven boat capsized on Tuesday evening being hit by a storm in the area, leaving the four traders missing.