Minister of Minerals, Energy, and Water Resources Ahmed Sow of Mali

Sow is suspected of conflict of interest involving a 3.

Britain's Times newspaper reported earlier this year that Sow received 315,000 pounds (400 euros, 540 dollars) for advising Fitina, a company in which he owned a 15 percent or more stake.

Mr Sow was travelling last week and could not be reached by the CDE spokesman, Valerie de Oliveira, who said his resignation had no connection to the Olaf inquiry.

Mr Sow is reported to have returned to the west African state.

While initially appointed to the post for five years, Mr Sow is understood to have stayed in contact with politics in Mali, where he has been tipped as a possible prime minister.