The statement said that Huma had been "relieved of his duties" as chairperson of the fund and its committees, on May 14, but not because of allegations of corruption or dishonesty.
However, the board did appoint a team of attorneys to investigate allegations raised by the chief executive officer, Humphrey Kgomongwe.
"The preliminary investigation into the allegations showed that Huma was not guilty of or a party to any corrupt or dishonest conduct," the statement read.
While the investigation was being conducted, Huma had been "exploring" another opportunity which "came to fruition" and required his full attention.
After hearing of the results of the preliminary investigation, he submitted his resignation.
"The board of directors wishes Mr Huma well in his future endeavours," the statement, faxed by a firm of attorneys, concluded.