Chinese police are investigating Ai Weiwei, the internationally-acclaimed artist, for "economic crimes", according to the state-run media.

In an official release citing information from China's Public Security Bureau, the Xinhua news agency reported that the 53-year-old Mr Ai was being investigated for "suspected economic crimes in accordance with the law".

The single-sentence, English-language report gave no further details and was deleted from the Xinhua website after an hour. It was the first concrete piece of news about Mr Ai since he was led away by police from Beijing airport on Sunday together with his friend, Wan Tao.

Meanwhile, Mr Ai's wife, Lu Qing, said the police had visited their home several times in the week leading up to his arrest and that Mr Ai had steeled himself for the worst.

"He felt a premonition that he would be detained," she said, in an interview with the Associated Press. "He told me something might happen to him". Mrs Lu said she has not heard from her husband since Sunday, but that some 40 to 50 policemen had subsequently raided their home and taken away both computers and money.