The board of directors of South African state-owned logistics firm Transnet said it had removed Chief Executive Siyabonga Gama, who has been accused of misconduct in a multi-million-dollar deal.
Transnet, which operates nearly three-quarters of the African rail network, the bulk of which is in South Africa, has been investigating allegations of corruption in the procurement of diesel and electric locomotives.
The board said late Sunday that it had lost confidence in Gama and that his last day as CEO would be Monday.
Gama was not immediately available for comment.
"We value and require transparency, accountability and expenditure that is cost-effective ... But we have found Gama's conduct – particularly during the investigation into the tender for new locomotives, with an inexplicable increase in excess of 9 billion rand ($627 million) in costs - to be incompatible with that culture," Transnet's board said.
Transnet is one of a handful of South African state firms that became embroiled in corruption scandals under former President Jacob Zuma.
However, Zuma has denied any wrongdoing and says he is the victim of a politically motivated witch-hunt, but new President Cyril Ramaphosa has launched an inquiry into allegations that tenders were awarded illegally during his predecessor's time in office.
($1 = 14.3462 rand)
(Reporting by Alexander Winning, Editing by Sherry Jacob-Phillips)