Welcome to Chidinmaokoye's Blog: Akinwumi Adeshina.

Mr Adesina is an eloquent advocate for Africa and the bank and a good fundraiser, but his detractors say he promises more than he delivers.

"His administration hasn't always been fantastic and perhaps he has run roughshod over some people. Maybe the practices haven't always been what they should be, and the feeling is that the board just whitewashed the investigation," the insider said.

Accused of favouring Nigerians

The whistleblowers also accused Mr Adesina of preferential treatment for Nigeria and Nigerians.

"I don't think we should trivialise the issues and reduce them to anti-Nigerian sentiment," said Ms Barungi, the Ugandan-born, Lagos-based former bank employee.

"It's really more about governance concerns that require attention and the investigation to help clear the air," she added.

Mr Araba, a Nigerian, said talk of the "Nigerianisation of the bank" was false as the country was under-represented in employee numbers despite being the largest shareholder.

As the crisis at the bank escalates, employees, consultants and government officials in African capitals, as well as American foreign policy nerds, wonder how this impasse will end.

But at the Treasury building right next to the White House, Mr Mnuchin and his advisors are doubling down.

"Undertaking an independent evaluation of facts is not at odds with a presumption of innocence, and by promoting transparency and good governance, it can only strengthen the AfDB's capacity to deliver results to people across Africa," the spokesman told the BBC.

Mr Adesina's carefully curated career could crumble if a new investigation criticises his reign at the AfDB. His style is solid, but the substance is now under scrutiny.

Akinwumi Adesina is a sharp dresser known for his expensive tailored suits, immaculate white shirts and an endless supply of colourful bow ties.

But the clean public persona of the 60-year-old president of the African Development Bank (AfDB) is now being questioned after a string of corruption and abuse of office allegations from his own staff spilled into the open. Mr Adesina has denied all the allegations.

The board of governors of the 55-year-old institution met on Tuesday to discuss whether to bring in an outside investigator into the allegations concerning the Nigerian's conduct just days after the US rejected an initial inquiry that cleared him.

The prospects of an independent probe comes only three months before he was expected to be re-elected unopposed at its annual general meeting in August.