Securities regulators cancelled thousands of trades in Canadian Oil Sands Ltd. (TSX:COS) Thursday after its plans to slash its dividend became public before a trading halt was imposed.

The Investment Industry Regulatory Organization of Canada (IIROC) says it cancelled thousands of trades in the company’s stock that occurred after the news was revealed. The regulator reports that shortly after 13:00 ET on Jan. 29 “material information pertaining to a dividend change became public, prior to the implementation of a trading halt.”

Specifically, the firm is cutting its planned dividend from 20¢ per share to 5¢, due to the impact of lower oil prices. While the regulator found that the news became public shortly after 13:00 ET, it says that trading wasn’t halted until 15:09 ET.

IIROC reports that its market integrity officials ruled that all trades which were executed after 13:04:56 ET be cancelled. It notes that the ruling affects 14,793 trades in the stock. “IIROC took this action to protect market integrity and to provide for a fair and orderly market for trading in Canadian Oil Sands,” it says.