Ai Weiwei said his wife had been summoned to a Beijing police station, becoming the latest person close to the Chinese artist and dissident to be pulled in for questioning. The 54-year-old said police ordered his wife Lu Qing, who is the legal representative of a company charged with massive tax evasion, to go to the station at 2:00 pm (0600 GMT) on Tuesday without explanation. \"I am very worried. She\'s a very innocent person. If I have done anything wrong, it has nothing to do with her. They should directly come to me, not to her,\" Ai told AFP. Ai, whose widespread activism has made him a thorn in the side of China\'s Communist authorities, disappeared into secret police custody for 81 days in April this year. After his release he was charged with tax evasion related to dealings by Fake Cultural Development, a company he founded but which is legally owned by Lu, and this month he was handed a bill for 15 million yuan ($2.4 million). Ai has denied the charges, calling them \"politically-motivated\", and said he intends to appeal. Within weeks of receiving the bill, he was able to pay an 8.45 million yuan guarantee needed to challenge the charge thanks to donations from fans. Lu has been questioned by police before, but this was the first time since her husband\'s release. Beijing\'s municipal police department would not comment on her case when contacted by AFP, and there was no answer from Lu\'s own number. In recent weeks, Ai said police had questioned two of his assistants, one of whom helped put together an exhibit in London\'s Tate Modern museum involving 100 million porcelain sunflower seeds. \"Several weeks ago, my assistant also got questioned for posting photos, and four days ago, another assistant who helped me do sunflower seeds also got a call from the Beijing police, telling him to go to the police station,\" he said. Ai said this month he had learned police were investigating possible charges of pornography against him, centred around pictures taken of the artist and four women, all naked. His problems with authorities started when he began investigating the collapse of schools in the 2008 Sichuan earthquake and a 2010 fire at a Shanghai high-rise that killed dozens. But until his detention he had been left relatively unscathed thanks to his family background. His father is the late Ai Qing, a famous poet who was disgraced and later rehabilitated by the Communist regime. Ai said Tuesday he had managed to speak to Lu by telephone. \"I\'ve called her and asked her what they\'re doing, and she said they\'re just asking her background -- where she comes from, which school she graduated from,\" he said. He added he had no idea whether the questioning was linked to the company involved in the tax evasion charges. \"We paid the bond, they seemed very happy with it, but maybe they\'re trying to threaten her, or to tell her authorities are there. I have no idea,\" he said.