Hong Kong's Securities and Futures Commission said 92% of Tse Sui Luen Jewellery's (HKG:0417) shares were concentrated in the hands of 21 holders as of Aug. 21, according to a Thursday Hong Kong bourse filing.

Shares of the jewelry company were up 25% in Friday's mid-day trade.

The regulator said Chairman and Chief Executive Yau On Yee and her spouse, Tse Tat Fung, controlled a combined 72.6% stake, while 19 other shareholders held 19.4%. That left only 8% of shares in public hands.

The stock jumped 236% in three days to HK$2.15 on Aug. 21, before easing to HK$1.51 by Sept. 3, still 136% higher than its Aug. 18 close.

The SFC warned that the company's share price could fluctuate sharply given the limited float.

In a separate filing, the company said it had not independently verified the regulator's findings on the minority shareholders but confirmed the insider holdings.

It added that, to its best knowledge, at least 25% of its issued shares remain in public hands, keeping the firm in compliance with Hong Kong listing rules.