Chandpur police Superintendent Md Amir Jafar said they had nabbed them during raids around the district lasting from Thursday night to Friday morning.
Among them, 15 were BNP activists and the rest Jamaat supporters, said police.
They were charged with committing acts of violence in several places, SP Jafar said.
Meanwhile, police filed a case in Wednesday night’s firebombing of a truck that killed the driver’s assistant in Chandpur’s Ghosherhat.
Chandpur Sadar police Sub-Inspector Md Abu Sayeed filed the case that charged 22 named persons, including district BNP Convener Sheikh Farid Ahmed Manik, and another 35 unknown persons.