Three people died after their motorcycle crashed into a utility pole and fell into a shrimp enclosure late on Wednesday.
The deceased are cousins Bayzid Hossain and Md Sakib, both aged 23, and their friend Zakaria, 22.
Babu, a friend of the deceased, said they had lost control of the bike. The three had been on their way home from a fair in Chandpai union, he added.
Locals took them to Mongla Upazila Health Complex, where the doctor on duty pronounced them dead, according to Babu.
Mongla police station OC Monirul Islam said they had confiscated the motorcycle.
