They have confessed, under primary investigation, to using a remote control-like device to detonate the explosives.
The arrestees were identified as Saifullah, 24, son of Ishak Mia, Emran, 25, son of Manir Ahmed and Abu Saleh, 25, son of Mahram Ali of Satkania upazila.
Tipped off, a team of CTTC unit conducted a drive in the area and arrested them from the spot on Sunday night, said Additional deputy-commissioner of CMP, Palash Kanti Nath while talking to reporters on Monday.
On February 28, five people including two policemen were injured in a bomb blast inside a traffic police box in city's Sholoshahar Gate-2 area.
Traffic sergeant Arafat Hossain Bhuiyan, ASI Md Alauddin and three other injured people were taken to Chattogram Medical College Hospital, said Assistant Prof Dr Rafique Uddin Ahmed, CMCH.