Five members of Bosnia's special police have been held over an armed raid on a bank van that netted 617,000 marka ($344,000; £241,000), officials say.
The suspects reportedly used automatic weapons and an anti-tank missile in the heist last September.
Their colleagues in the police helped identify them to investigators, said Dragan Lukak, interior minister of Bosnia's Serb-run region.
Two other people have been arrested for alleged involvement in the raid.
Money on board the armoured vehicle belonged to a subsidiary of UniCredit, Italy's top bank. A security guard was injured in the robbery.
Mr Lukak said the suspects, if found guilty, would have "disgraced... their unit and the whole police force".
Bosnia is administered under two entities, the Muslim-Croat Federation and the Serb Republic, each with their own police force.