Alexandre-Ferdinand Nguendet said he was issuing a warning to militiamen and looters that in his words, the party was over. Paul Wood reports from Bangui.
A representative for the charity said that people whose homes had been submerged were living in boats and trying to protect their roofing material from looters.
The fear now is that, since the pieces are too recognisable to be sold intact, the robbers will break out the diamonds and sapphires to flog them separately.