BEIJING (AP) — Chinese authorities have charged rights activist Jiang Tianyong with subversion of state power, six months after he disappeared and lost contact with his family and lawyers, his wife said Tuesday.

Prosecutors in the central city of Changsha sent the family a notice of the charge dated May 31, Jin Bianling told The Associated Press. That marked the first official confirmation of Jiang’s whereabouts since he was taken away by state security agents in late November.

Vaguely defined subversion charges are frequently leveled against human rights activists and perceived political foes of the ruling Communist Party. Convictions, which are a virtual certainty, sometimes lead to prison sentences of a dozen years or more.

Jiang previously worked with foreign media and rights groups to publicize the plight of China’s human rights lawyers, many of whom were detained in an intense crackdown launched in July 2015. U.N. representative on human rights Philip Alston said in a report this month that he believed that Jiang and other people he spoke to last year during a visit to China had suffered official reprisals.

In Washington, State Department spokeswoman Heather Nauert called the subversion charge against Jiang “another troubling sign” of China’s crackdown on lawyers and human rights activists. Speaking to reporters, she urged the government to immediately release Jiang and drop charges against him.

In March, Chinese state media reported that Jiang was being held at a secret location on suspicion of “inciting subversion of state power,” a lesser charge usually given to those who comply with the demands of the authorities. Jin said that the state may have ultimately brought the more serious subversion charge against Jiang because he has not cooperated adequately while in detention.

The Changsha Intermediate People’s Court declined to comment on Jiang’s case, saying only family and lawyers can seek information about specific cases. No trial date has been announced.

In recent months, lawyers and human rights activists facing grave charges have been released after perfunctory trials – but only on condition that they admit to the charges against them and make public displays of repentance and subservience to government authority.

Last month, the authorities released activists Xie Yang and Li Heping following two-year ordeals after they admitted to the subversion charges against them.