Shares in luxury goods group LVMH briefly fell almost 9% at the open on Monday before recovering in what traders said was likely a "fat finger" erroneous trade.
The shares on Paris' CAC 40 opened at €310.45 and fell to €285.7, their lowest since 12 February in the opening minutes.
The stock then recovered most of the lost ground and was at €313.3, down 0.1%, at 0939 GMT.
Turnover in the stock was unusually high, with almost 200,000 shares traded in the first 75 minutes after the opening bell, 28% of its 100-day average daily total.
LVMH and Euronext, which operates the CAC 40 stock exchange, were not immediately available for comment.
"It was probably a fat finger right at the start of trading," said a Paris-based trader.
"No one understood what happened. It was likely a mistake," said another trader.