By David Bamford
BBC News Africa editor
Police in Burundi have arrested central bank governor Isaac Bizimana for allegedly embezzling state funds.
Burundi is only now emerging from a bitter civil war
Officials said the government lost millions of dollars when an oil importing firm was overpaid.
The payment was to reimburse the firm, Interpetrol, for losses it incurred prior to 2002 when Burundi was under blockade because of a military coup.
Mr Bizimana's lawyer could not immediately be reached to comment on his arrest.
Prosecutors said he had authorised a payment of $21m (£10.3m) to Interpetrol, several times what it was due.
A former finance minister, Denise Sinankwa, is also under investigation.
She has denied any wrongdoing.
The scandal comes as Burundi is awash with political disputes at senior levels.
There is also a threat that the civil war could re-ignite through the lack of a political agreement.
A former rebel leader, Pierre Nkurunziza, is now president.
But even he has been unable to persuade the last of many rebel groups, the FNL, to sign up to a peace settlement.
Despite this, the settlement has been remarkably successful - bearing in mind the ethnic trauma of the past.