Police also seized Tk14,000 and a motorcycle from their possession
The imposters were produced before a court, which sent them to jail on Friday.
The arrestees are Zainuddin Bishwas, 48, Milton, 35, Hasan, 37, Tayeb Ali, 48, and Arifuzzaman, 47.
Police also seized Tk14,000 and a motorcycle from their possession, Kaliganj police station Officer-in-Charge (OC) Mahfuzur Rahman Mia said.
He said: "A van driver named Pradip Das was going to Naldanga upazila to sell potteries on Thursday. The imposters stopped him near Kaliganj-Naldanga police box, and demanded Tk30,000 to release him."
"Pradip immediately sent them Tk14,000 through bKash and left the scene," he added.
Later, Pradip filed a case with Kaliganj police station over the matter. Police tracked down the bKash transaction number and arrested three of them.
In primary interrogation, the arrestees revealed the location of other two fake DB officials. Later, police arrested the duo on Thursday night.