Apple registered 1.5 million shares to Jobs last May, part of the $430 million sale of his company, Next Software, to Apple. Under the terms of the deal, Jobs can trade his shares at any point.
"We were told 1.5 million shares were sold as a block," said Nancy Paxton, an Apple investor relations spokeswoman. "We don't know if it was Steve...I'm not aware of anyone speaking with him to ask."
Jobs did not return calls to his office at Pixar Animation Studios.
In published reports, Jobs has indicated that he had no intention to sell his shares. Jobs, who held one share of Apple before the Next deal, received a 1.19 percent stake in Apple upon receipt of the stock.
Paxton said the company has a insider trading policy that advises company executives and directors to avoid buying and selling Apple shares during certain periods of the quarter. The current policy asks that officers and directors refrain from selling shares between June 1 through July 16, when the company reports its third-quarter results.
In heavy trading yesterday, Apple's shares fell to 14-11/16, down 7/16 over Wednesday and near its 52-week low. More than 3.4 million shares traded hands, nearly double the average trading volume.
The stock closed today unchanged from yesterday and resumed a more normal trading pattern.
The computer maker, which has seen its stock plummet to a ten-year low, posted a whopping loss of $708 million in the second quarter, rivaling its historic loss of $740 million a year ago. And it reported declining quarterly revenue of $1.6 billion for the second consecutive quarter.
Apple will report its third-quarter performance on July 16.