Shares in Energy Resources of Australia (ERA), which operates the Ranger uranium mine in Kakadu, are soaring.
A short time ago, the shares had gained 24.2% to $0.41.
The company was pinged by the ASX, asking if it had any information to explain the sudden rise in the share price.
Energy Resources of Australia had no explanation, saying it had no information which had not already been announced to the market.
The company last month posted a half year net loss of $255 million, including write downs of $197 million.
Energy Resources of Australia, with its major shareholder Rio Tinto, has put on hold its plans to expand the Ranger mine in Kakadu because of uncertainty over the market for uranium.
The traditional owners, the Mirarr people who are paid 4.25% of gross revenue from the mine, want to eventually see the mine area incorporated into Kakadu National Park.