Rajibull Mollah, resident of Raningar village in the district, was arrested for a petty crime from a country liquor den and taken to Raninagar police station yesterday.
Mollah was found hanging in the police station lock-up last night, police said adding that he allegedly committed suicide.
The body has been sent for postmortem, police added.
Meanwhile, West Bengal Pradesh Congress Committee chief and Union Minister Adhir Chowdhury alleged that Mollah was beaten to death by police.
Chowdhury also claimed that Mollah was Congress supporter.