THIRTEEN people have been arrested following an investigation into a bizarre multi-million-dollar scam in which victims were tricked into believing worthless pieces of black paper were US$100 banknotes. One victim lost foreign currency worth more than $2.5 million. Commercial Crime Bureau officers are trying to trace a number of victims they believe have not reported their losses. The conmen targeted executives staying in some of the territory's top hotels. They showed the victim a suitcase full of neatly packed bundles of black paper which they claimed were US$100 notes that had been shipped from Africa. The victim was told each note had been blackened using a hi-tech process to make transport less risky. The tricksters said they were executives of an African nation's central bank. In some cases, they tricked people who had already lost money in previous scams. A victim was contacted and told that his lost cash had been found, but in this security-blackened form. The victim was told that special and expensive chemicals from Switzerland were needed to clean the notes. To prove it, one was taken from the top, carefully cleaned with a mysterious-looking chemical, and shown to be a US$100 note which the victim was invited to take to a bank to have it authenticated. The victim was asked for between US$100,000 and US$900,000 to buy extra supplies of the chemical on the understanding that a proportion of the cleaned cash, said to total more than US$10 million, would be given in return. After collecting the money from the victim, the tricksters left behind the suitcase full of the 'blackened cash', promising to return with the chemicals. But they never returned. When the victim finally examined the notes, he discovered they were nothing more than black pieces of paper and all his cash had bought was a suitcase and some raw materials for starting a barbecue. So the victim lost more money in payments for phoney cleaning chemicals. 'It sounds amazing, but it has been very successful,' one officer said. Bottles of the 'cleaning chemical' are being analysed by the government chemist. The instructions for performing the blackening and cleaning of the real US$100 can be found in books of conjuring tricks.