The heaviest turnover in Icon prior to this surge was in May, when just over a million shares were traded. Yesterday's turnover exceeded 8 million shares.

Company secretary John Cummins said the buying was from one of the directors who was increasing his stake in the company.

"Obviously it is one of the directors increasing his holding in the company. The order is incomplete at this stage and unpaid for, so I can't reveal the identity of the director," he said.

The incomplete status of the order meant that more buying was probably ahead for the stock, which had turned over around 300,000 at press time on Wednesday. Cummins said he was unaware of the size of the order.

Managing director Ray James was in the United States and could not be reached for comment.