Nairobi, Feb. 3 -- As the world toasted Nigeria's Olugbenga Agboola as Africa's freshly minted tech billionaire, Kenyan authorities were investigating his firm for possible money laundering links.

It was February last year when a firm he co-founded - Flutterwave - was valued at $3 billion, making it the most valuable start-up in Africa as international investors bet on the continent's fintech scene.

While this made the 37-year-old Agboola one of Africa's most well-known entrepreneurs, investigators and regulators in Kenya suspected his Nigerian payments company was riding on proceeds of crime, in particular card fraud.

In the end, the High Court froze its Sh6.2 billion spread in 62 bank accounts on money laundering fears and the Centra...