On 3 April 2011, Ai was arrested at Beijing Capital International Airport just before catching a flight to Hong Kong and his studio facilities were searched. A police contingent of approximately 50 officers came to his studio, threw a cordon around it and searched the premises. They took away laptops and the hard drive from the main computer; along with Ai, police also detained eight staff members and Ai's wife, Lu Qing. Police also visited the mother of Ai's two-year-old son. The Chinese Ministry of Foreign Affairs said on 7 April that Ai was arrested under investigation for alleged economic crimes. Then, on 8 April, police returned to Ai's workshop to examine his financial affairs. On 9 April, Ai's accountant, as well as studio partner Liu Zhenggang and driver Zhang Jingsong, disappeared, while Ai's assistant Wen Tao has remained missing since Ai's arrest on 3 April. Ai's wife said that she was summoned by the Beijing Chaoyang district tax bureau, where she was interrogated about his studio's tax on 12 April. "South China Morning Post" reports that Ai received at least two visits from the police, the last being on 31 March – three days before his detention – apparently with offers of membership to the Chinese People's Political Consultative Conference. A staff member recalled that Ai had mentioned receiving the offer earlier, "Ai didn't say if it was a membership of the CPPCC at the municipal or national level, how he responded or whether he accepted it or not."