Beijing last night said police were investigating maverick artist Ai Weiwei for suspected economic crimes - the first official confirmation of his detention since he was stopped from boarding a flight to Hong Kong four days ago.
A brief Xinhua statement, released after midnight, did not give further details about the investigation, but it is a sign the authorities may prosecute the internationally renowned artist - formerly considered untouchable because of his fame and his family background.
Police have 30 days to decide whether to charge Ai. Liu Xiaoyun, a lawyer friendly with Ai, said police had broken the law by not explaining Ai's detention within 48 hours.
He has not been seen since Sunday, when border police stopped him at Beijing's airport.
Ai, China's most famous contemporary artist and co-designer of Beijing's Olympic stadium known as the 'Bird's Nest', has emerged in the past two years as a vociferous critic.
Yesterday, state-controlled newspaper the Global Times began to build a legal case for Ai's detention.
'Ai Weiwei does as he pleases and often does what others dare not,' the newspaper said. 'He himself probably realised that he was never far away from the red line of Chinese law. So long as Ai continued, it was possible that he would breach the line one day.'