The JSE will investigate Aspen Pharmacare after the drugmaker's shares fell to their lowest in five years after a conference call it hosted last week.
"The exchange's market regulation division is reviewing trading ahead of the conference call and the subsequent decline in Aspen's share price" on June 27, the bourse said.
"If there is any trading that it believes warrants further investigation, this will be referred to the directorate of market abuse at the Financial Services Board, as is standard practice."
Aspen investor Owen Nkomo is to complain to the JSE about the price drop.
Aspen's stock price fell 6.2% - the biggest decline since April 2009 - to R288 on Friday, the day of the call.
