Authorities in the northern port city of Tianjin have confirmed that a second activist who tried to help the son of two detained human rights lawyers to flee China is also being held in the city, with no access to a lawyer. Rights activist Tang Zhishun is being held in the Tianjin No. 2 Detention Center on suspicion of "organizing the smuggling of persons across a national boundary," his lawyer Tan Chenshou told RFA on Friday. The family of fellow activist Xing Qingxian received official notification of his criminal detention on identical charges at the same facility earlier this week. Tang and Xing were detained more than seven months ago in northern Myanmar, as they posed as tourists to escort Bao Zhuoxuan, the 16-year-old son of detained rights lawyers Wang Yu and Bao Longjun, across the border. But Bao and his minders were found out, and taken away from the Huadu Guesthouse in the border town of Mongla on Oct. 6. The boy's passport had been confiscated by Chinese police shortly after his parents' detention, and he was unable to pursue plans to attend school in the United States. July 9 lawyer crackdown Bao has been staying with his grandparents near Beijing since his detention in Myanmar. His parents were detained on the night of July 9, 2015, at the start of a nationwide police operation targeting the legal profession. Tan said he had applied to be officially recognized as Tang's lawyer, but the authorities had refused, saying that Tang would "hire his own lawyer." "I tried to get myself registered as his lawyer, but they clearly acted against the Criminal Procedure Law's provisions for the right to a legal defense," Tan said. "They are in breach of the specific clauses relating to the hiring of lawyers, and they are in breach of fundamental rights to a lawyer in the United Nations human rights covenants," he said. The overseas-based Chinese Human Rights Defenders (CHRD) network called on the ruling Chinese Communist Party to release Xing and Tang immediately. "They have been detained as political persecution for their activism, including their efforts to rescue Bao Zhuoxuan from house arrest," the group said in a statement on its website. "They are highly vulnerable to ill-treatment, including not having access to necessary medications," it said. Rights training for evictees Tang, 40, was a former engineer who became involved in civil rights work after his home was demolished in 2006. He has since trained evictees and villagers under threat of demolition how to defend their rights, and co-founded a public interest non-government group, CHRD said. Meanwhile, Xing's lawyer Gao Shengcai said he had been denied permission to visit his client when he visited the detention center on Thursday. "They used every kind of excuse, and then they closed for the day," Gao said. "It's clear that their whole aim was to prevent me meeting with Xing." Calls to the Tianjin No. 2 Detention Center rang unanswered during office hours on Friday. China has detained, questioned or otherwise placed restrictions on at least 319 lawyers, law firm staff, human right activists and family members since the July 9 crackdown began, a Hong Kong-based rights group reported on its website. At least 23 have been criminally detained or formally arrested on subversion, state security or public order charges, while others have been banned from leaving the country or placed under house arrest or other forms of surveillance, the Chinese Human Rights Lawyers Concern Group said.