Shares in troubled miner Glencore surged as much as 72 per cent to HK$18.36 during trading in Hong Kong today.
In a statement this morning, the company said it was "not aware" of any reason behind the price rises.
The board confirms that it is not aware of any reasons for these price and volume movements or of any information which must be announced to avoid a false market in the company's securities or of any inside information that needs to be disclosed under Part XIVA of the Securities and Futures Ordinance (Chapter 571 of the Laws of Hong Kong).
The company's share price has been volatile in recent weeks, as investors became nervous of the company's large debts in the face of plummeting copper prices.
That led various directors of the company to shore up its share price by buying vast chunks of stock. On Friday non-exec director William Macaulay bought 1.7m shares, worth £1.5m, two days after chairman Tony Hayward hoovered up 100,000 shares at 91p per share.
London-listed shares in the company rose 10 per cent to 104.5p in the first minutes of trading.