UK police investigating the murder of a boy whose torso was found in the River Thames two years ago say they are a step closer to bringing charges.
They suspect the boy, who was named Adam by officers, was the victim of a ritual killing after being brought to Britain from Nigeria. His torso was found near Tower Bridge in September 2001.
A file is now being prepared for the British Crown Prosecution Service, raising the possibility of extraditing suspects from more than one country.
Commander Andy Baker of the Metropolitan Police told BBC Radio 4's Today programme: "We are putting together an advice file now on the circumstantial evidence we have got so far. We are very optimistic, we will not give up, we are determined.
"We must keep an open mind. It could be that the motive was purely domestic. But we do believe 99.9% it was of a ritual nature, it was very macabre, extremely violent."
Detective Inspector Will O'Reilly, of the London Metropolitan Police, is leading the inquiry. He said he has never given up hope of solving the crime. He told the BBC: "We have got a lot of circumstantial evidence. You are always optimistic. I knew it was a challenge.
"According to the FBI and people we spoke to in the early days, this was almost unsolvable. You did not know who the victim was, when it happened or how it happened."
Officers have visited Nigeria during the investigation. By analysing the mineral content of the boy's bones, forensic scientists concluded he had been brought up in a particular part of Nigeria.
New evidence found in the boy's lower intestine was identified by a botanist at Kew Gardens as being the highly poisonous calabar bean - given to suspected witches in West Africa.
The bean may have been used to subdue Adam before his death, British police said. Detectives think Adam was aged between four and six, and was alive when he arrived in London.