According to lawyer Mo Shaoping, Yang’s family had received a written notice from Beijing’s State Security Bureau confirming the writer’s detention.
Mo said he would be filing a petition to meet his client but wasn’t sure if it would be allowed, due to the nature of the charges against Yang.
The Australian Department of Foreign Affairs and Trade said in a statement they would continue to seek confirmation as to why Yang had been taken and would attempt to obtain consular access to him “as a matter of priority.”
Yang, 53, is novelist and writer who previously worked as an official with the Chinese foreign ministry.
Though Yang holds Australian citizenship, he is known to spend most of his time in the United States, where he is a visiting scholar at Columbia University in New York.
Yang had made a trip back to China from New York with his wife on January 17, to pick up his step-daughter’s US visa, family friend Watson Meng told CNN.
Meng said he tried to get in touch with Yang on social media the day after he arrived, but noticed he hadn’t read the posts days later. He then said he learned Yang had been detained through sources in the security department.
Yang has an active Twitter account with more than 130,000 followers, to which he routinely posts satirical commentaries that are critical of the Chinese government.
Authorities in Beijing have yet to officially confirm Yang’s detention. During a regular press briefing, Wednesday, Chinese Ministry of Foreign Affairs spokeswoman Hua Chunying said she was unaware of Yang’s case.
Australian authorities couldn’t confirm the date Yang was taken in custody, or where he was being held.
Relations between Australia and China had been slowly warming after a deep chill in early 2018 following Canberra’s drafting of strict foreign interference laws, which officials in Beijing believed were targeted at China.
Elsewhere Beijing has been cracking down on individuals it views as a threat to the Chinese government, including labor activists, human rights lawyers and international bloggers.
Yang has a complicated history with Beijing, owing to his background as a former government official. He is known to have vanished in China once before, in the spring of 2011. Although it was widely speculated he was detained by Chinese state security agents, he never confirmed it upon re-appearing.
“If the system has swallowed this hugely popular commentator … are there no longer any limits?”
CNN’s Serenitie Wang contributed to this article.