Shares in vitamin maker Blackmores were falling on reports of more Chinese government intervention in online sales of foreign goods.
A short time ago, they were down $22 to $181.140, a fall of more than 11%.
A new 11.9% value-added tax on foreign goods bought online came into force on Friday.
There are also reports the finance ministry will be stricter on which goods bought online can be imported through free trade zones in 12 cities.
Much of Blackmores product reaches China via resellers who buy in Australia and sell in China online.
Blackmores in February posted a record half-year profit of $48 million, a rise of 160%, on scorching demand for its vitamins in China and Asia.
Sales to Chinese consumers, both direct and through Australian retailers, represents about 40% of group revenues.
Blackmores is one of a group of Australian companies, including infant milk formula companies a2 Milk company and Bellamy’s, whose products are in high demand in China.
a2 Milk shares were down 2% to $1.705. Bellamy’s was down 0.3% to $10.01.