Johannesburg - Shares of South African technology firm Pinnacle Holdings are down sharply after financial services regulator confirms it is investigating potential insider trading in its shares.

Pinnacle shares are trading 5.55 percent lower at 13.45 rand, making it the biggest decliner on the All-share index, which was down 0.5 percent.

A Pinnacle director, Takalani Tshivhase, was arrested in March on charges he offered a bribe to a senior police official in order to win a contract for the company, a charge he has denied.

However the company waited 20 days to disclose the arrest, during which time Tshivhase and other directors sold Pinnacle shares. - Reuters