One Australian was detained in Hong Kong under the new national security laws there, a Senate committee has been told.
It is believed the person was released after a few days but further information is being sought, a foreign affairs official told an estimates hearing on Thursday.
It is currently unknown whether the Australian consulate in Hong Kong was notified.
Justin Hayhurst, assistant secretary of DFAT's Indo-Pacific group, said Australia is worried about the "systematic unravelling of democratic institutions" in Hong Kong.
Under the law, some cases can be tried in mainland China and Beijing has power over how the law is interpreted, raising concerns about Hong Kong's independence and freedoms.
Mr Hayhurst said China was dismissive of Australia's concerns over the law when they were raised.
"In their view this is not a matter in which we have any standing," he said.
