Police could not unearth the mysterious death of an elderly trader, found with severed head, in Rajapur upazila on Monday yet.
The deceased, Habibur Rahman, 60, was son of late Khorshed Ali of Al-Falah village in Kathalia upazila.
Meanwhile, police detained Habibur's four other co-passengers and the driver of the three-wheeler he was travelling on and interrogated them at Rajapur Police Station on Monday night, Officer-in-Charge Shamsul Arefin of the police station said.
During interrogation, they all informed that the scarf around Habib's neck got entangled with the engine of the vehicle but none of them noticed that.
They noticed the incident when Habib's severed head fell in front of them, police said, quoting one of the passengers Abdul Haque.
When asked why they fled the scene, they said seeing the horrifying incident they thought Habib might have been attacked by a ghost.
Although police primarily accepted their statements, the mystery will be solved after getting the autopsy report, the OC said.
The four arrestees were released after giving an undertaking, but driver Hanif is still under police custody.