Kenyan police have confirmed they are carrying out DNA tests on a man suspected of being the most wanted criminal from the Rwandan genocide.
The man was arrested on Friday in one of Nairobi's plush suburbs and is being held for questioning.
Police say it could be Felicien Kabuga, a Rwandan businessman accused by the International Criminal Court of being a key financier of the Rwandan genocide.
Some 800,000 people were killed in just 100 days in the 1994 genocide.
Police are keeping tight-lipped about the details of the suspect but a senior police officer has confirmed to the BBC that a man arrested on Friday is undergoing forensic tests to try to verify his identity.
They are seeking to establish whether the man they are holding is Mr Kabuga, a man with a $5m (Â£2.4m) bounty on his head.
He is accused of being one of the key figures behind the 1994 genocide in Rwanda where some 800,000 Tutsis and moderate Hutus were killed.
In the past the Kenyan authorities have been accused of harbouring alleged war criminals and have been threatened with action from the UN security council.
Last month a Kenyan court froze the assets of Mr Kabuga who has a number of business interests in the Kenyan capital and who has been spotted with his bodyguards on several occasions.