The body was found without a head

Nigerian Sam Onogigovie, 37, was taken into custody in Dublin on Wednesday under an extradition warrant issued by German police.

Officers from the Garda are searching an address in the Irish Republic's capital.

They also hope to take a DNA sample to compare it with the boy's, whose headless and limb-less body was found near Tower Bridge in September 2001.

Detectives believe Mr Onogigovie could be a close relation, or his natural father.

Mr Onogigovie is believed to be the estranged husband of a woman who was arrested in connection with the case in Glasgow in July last year.

Human trafficking

She was later sent back to her home country of Nigeria.

Mr Onogigovie was jailed for seven years in his absence in Germany in March 2001 for forgery, claiming residence and crimes linked to people trafficking.

He is due in court on Thursday.

Describing the arrest as "highly significant" Commander Andy Baker said officers had been trying to trace him since the arrest in Glasgow, but he had been living under a false name.

Commander Baker said he believed more than one person may have been involved in the killing.

Although he is thought to have been murdered in London, forensic examinations found the boy, dubbed Adam by police, lived in a rural area in south-west Nigeria.

Detectives think he was aged between four and six, and was the victim of a ritual killing.

Mandela appeal

A major police investigation has taken detectives to Nigerian villages where they made house-to-house inquiries to try to find his parents.

Nelson Mandela also appealed for information, which was translated into Yoruba, the local language, as has Arsenal's Nigerian star Nwankwo Kanu.

Last week detectives said DNA tests developed to identify 11 September victims could help to trace Adam's killer.

Bone fragments used in a potion the youngster swallowed shortly before he died have been submitted to New York's medical examiner.

It is hoped the new techniques will help them identify the witch doctor who created the concoction.

The brew, which was found in the boy's lower gut, also contained quartz, clay pellets and very small samples of rough gold.

Pollen samples found in Adam's stomach showed that he was alive when he arrived in London.

It is believed he was murdered a few days later.