The PIC, which has nearly 2 trillion rand ($147 billion) of civil servants' pension under its custody and is Africa's biggest pension fund, said it would immediately conduct an forensic investigation into the allegations.
The PIC said in a statement it would appoint a senior lawyer to help the board with the investigation, but did not disclose the allegations.
Matshepo More, the acting CEO, could not be reached for comment.
The PIC deputy chairman Xolani Mkhwanazi said an email by the anonymous whistle blower did not name the two other non-executive directors implicated in the allegations.
The new allegations come as a judicial inquiry into the firm continued to hear evidence from its staff members.
The inquiry was set up after allegations that PIC's former chief executive Dan Matjila had misused funds and made careless investment decisions.
Matjila, who stepped down in November last year, has denied any wrongdoing.
The PIC is the biggest investor in South Africa’s economy, holding a large volume of bonds issued by government and state-owned firms, as well as stakes in blue-chip companies such as miner Anglo American, lender Absa and telecoms giant MTN Group.
($1 = 13.5961 rand)
(Reporting by Tiisetso Motsoeneng; Editing by James Macharia)
