The stock will be kept at the court’s evidence room in the port city until it goes under the hammer on Thursday afternoon.
Police on Monday night arrested four people on charges of selling the TCB onion in the black market and seized the stock at Jahangir Store in the Oxygen area.
The four are TCB dealer Dolon Barua, his associates Dilip Barua and truck driver Emdadul Haque, and customer Mohammad Jahangir.
They landed in jail after police produced them in court on Tuesday.
Police also submitted the onion to the court as evidence, Bayezid Bostami Police Station OC Priton Sarker told bdnews24.com.
A three-member committee has been constituted for the auction.
The government is selling onion at fair prices through TCB dealers in a bid to control skyrocketing prices.