Police investigating the murder of a boy whose torso was found in the Thames have arrested 21 people in raids across London.
Police raided nine homes across London
Nine addresses in east and south-east London were searched by nearly 200 Metropolitan Police officers on Tuesday morning.
Ten men and eleven women were held by police. A baby belonging to one of the women was also taken into care while the woman was being questioned.
Among the items found was the skull of an animal which had a nail driven through it.
Commander Andy Baker, from the Metropolitan Police, said: "Some of the items would raise a few eyebrows - they look like some element of ritualism is involved."
Most of those arrested were for immigration offences, identity fraud and passport forgery.
The police were acting on information from detectives who have been investigating why the limbless and headless body of a boy ended up in the Thames.
The victim, called Adam by officers, was found in the river near Tower Bridge in September 2001.
Police suspect that he was a victim of ritual killing after being brought over from Nigeria.
Officers travelled to the African country after forensic tests showed he was from the area around Benin City.
All of the people arrested on Tuesday are from the same part of Nigeria and police want to compare their DNA with Adam's to see if any are related to him.
Police are also looking at their connection with a Nigerian man arrested in Dublin earlier this month in connection with the investigation.
Sam Onogigovie, 37, was held under an extradition warrant issued by police in Germany, where he has been convicted of crimes linked to human trafficking.
Detectives from Scotland Yard also questioned him about the murder of Adam.
Tuesday's arrests were made by officers from Operation Maxim, the multi-agency unit tasked with targeting organised criminals who are in the UK illegally.
The body was found without a head
Detective Inspector Will O'Reilly, leading the Adam inquiry, said: "We've uncovered what we believe is a criminal network concentrating on people trafficking.
"We are convinced that we are on to a group, or individuals, that were involved in trafficking Adam into the country."
Police also said there was evidence of children having been at the raided addresses.
Detectives think Adam was aged between four and six, and was alive when he arrived in London.
They are also trying to trace the witch doctor who brewed a potion containing bone fragments which the boy swallowed before he died.
The fragments have been submitted to New York's medical examiner who will use techniques developed to identify September 11 victims.
"Interesting substances" found in the raids will also be compared with the potion found in Adam's intestines.
Police think some of the items confiscated could be linked to rituals.