A Chinese musician arrested on public order charges for singing about late Nobel peace laureate and political prisoner Liu Xiaobo has been sent to hospital, sparking concerns that he may have been tortured or mistreated while in a police detention center. Singer-songwriter Xu Lin was detained by authorities in the southern province of Guangdong after he penned songs in memory of Liu, who died in police custody of late-stage liver cancer in July. "I was informed by staff at the detention center on Friday that Xu Lin had been sent to the People's Armed Police Hospital," Xu's wife, who gave only her surname Wang, told RFA. "They said he hadn't been eating well in detention, and I said there is something wrong here;[the staff member] went quiet, then said they didn't know," she said. "When he went there, he was lively enough, and now they're telling me he's in hospital?" Wang said Xu hasn't suffered from any major health problems in more than a decade of marriage. She fears the visit is the result of torture or mistreatment in detention. "How could he have wound up like this without being tortured?" she said. Xu Lin was formally arrested for "picking quarrels and provoking trouble" on Nov. 2. His case was handed over to the state prosecution service in January, which sent it back to police "for further investigation" in April. He requested not to have a lawyer, following a pattern set by other detained activists who strike a deal to plead "guilty" in return for more lenient treatment, although his associates said he simply had no wish to take up valuable resources. London-based rights group Amnesty International has previously warned that Xu Lin is at risk of torture and other ill-treatment. "The investigation started over after the prosecution sent the case back to police in April," Wang said. "Since then, there has been no news. They just keep telling me I need to cooperate, and he'll be home in no time." Wang said the state security police had visited her at the end of last month and searched her phone, finding that she had been in touch with human rights campaign group Rose China. "Some of the names ... in there were pretty sensitive, and they told me to delete them, so I agreed," she said. "Then, there were some people watching us around the May 1 holiday, but I don't know why that was." Lawyer Lin Qilei said the singer-songwriter was likely being held in connection with song he wrote for Liu Xiaobo. Liu Xiaobo died weeks after being diagnosed with late-stage liver cancer, and repeated requests from his family to seek medical treatment overseas were ignored. Activists who staged memorials Police have since detained a number of activists who staged memorials in Liu's honor, including Zhuo Yuzhen, detained in Guangdong's riverside town of Jiangmen for taking part in a seashore memorial a month after Liu's passing. His wife Liu Xia, who has never been charged with any crime, remains under house arrest and continual police surveillance in spite of continued international calls for her unconditional release. Germany-based writer Liao Yiwu, who has been liaising with the German government in a bid to secure Liu Xia's release and permission to leave China, said she remains under close surveillance by state security police in spite of having been told she would be allowed to go overseas. "Liu Xia told me[by phone on May 12] that there is a police car downstairs, and they insist on taking her wherever she wants to go, then they wait," Liao said. "She asked if she could go to make a passport application, but the driver wouldn't give her an answer. The guy who used to answer[her questions] seems to have disappeared." Independent Chinese PEN president Tienchi Martin-Liao said she fears that Liu, who has been suffering from severe depression since her house arrest began in 2010, could also die in police custody. "I am still very worried about the medication she is taking, because she doesn't go to fill the prescription herself," Martin-Liao said. "The state security police deliver the medication ... I think that this government ... would stoop to anything." "She really needs to get out of there very soon; she is really at risk if she doesn't," she said. A group of French and German diplomats tried to visit Liu Xia on Friday following concerns about her health, but were refused entry by officials at the gate of the residential complex in Beijing where she lives, according to recent media reports.