The lawyer and niece of detained rights lawyer Pu Zhiqiang has been placed under criminal detention herself, a veteran lawyer said yesterday. The detention of Qu Zhenhong and two other associates close to Pu has stoked fears that police are collecting further evidence to prosecute the prominent lawyer well known for his defence of sensitive cases. The lawyer, Zhang Sizhi, said he did not know the reason for the detention. It is also unclear when Qu was taken into custody, although several activists have posted messages on Twitter suggesting she was detained on Tuesday for "illegally obtaining personal information". Police this week detained a Chinese employee of Japan's Nihon Keizai financial newspaper, and a Beijing-based NGO worker and former journalist, both of whom are close to Pu. Pu, 49, who took part in the Tiananmen pro-democracy protests in 1989, was detained last week for "picking quarrels and provoking trouble" after attending a May 3 event marking the 25th anniversary of the crackdown. Four others - scholars Xu Youyu and Hao Jian , the activist writer Liu Di and house church leader Hu Shigen - were detained on the same charge after attending the event, which took place at a private residence in Beijing. Pu's detention surprised many as he had dealt with the authorities for years and was confident in his handling of sensitive rights cases. He has been openly critical of ex-security chief Zhou Yongkang, who is believed to be the subject of a graft investigation. But Teng Biao, a visiting law scholar at the Chinese University of Hong Kong, said: "Nobody can be sure of where the boundaries are unless you steer clear of human rights and sensitive issues … it's all up to the authorities." Teng said he believed the authorities' threshold for tolerating dissent had fallen markedly since last year, when scores of activists were arrested, including some from the New Citizen movement.