Groundbreaking Chinese artist Ai Weiwei appeared healthy but tense during his first meeting with family since he was detained more than a month ago, and authorities still haven't explained why he was seized, his wife said Monday.

Lu Qing told The Associated Press she was allowed to meet with her husband at an unknown location for about twenty minutes Sunday afternoon and that he seemed conflicted and upset, though insisted he was healthy and that his physical needs were being met.

"I could see redness in his eyes. It was obvious that without freedom to express himself he was not behaving naturally even with me, someone from his family," Lu said.

The avant-garde artist and fearless government critic was taken into custody April 3 and has been held incommunicado though not yet charged with any crime. His case has prompted an outcry in the art world and among officials in the U.S. and EU who say his treatment is a sign of China's deteriorating human rights.

The Foreign Ministry has said Ai is being investigated for suspected economic crimes, but his detention comes amid a crackdown on dissent apparently sparked by fears that uprisings such as those in the Arab world could erupt in China. Ai had been keeping an informal tally on Twitter of the dozens of bloggers, writers and other intellectuals who were detained or arrested in the campaign before he was taken away.

Ai is famous in artistic circles for performance pieces that explored the dizzying change of contemporary China and for irreverent, avant garde works such as a photo series that shows him giving the middle finger to landmarks such as Tiananmen Square in Beijing and the White House in Washington.

He is known more popularly as one of the designers on the iconic "Bird's Nest" national stadium for the 2008 Beijing Olympics, and in recent years, has emerged as an advocate for victims of social injustice.

Lu said two other people were present during the brief meeting, including one person "who seemed to be in charge of Ai," and another who took notes.

"He seemed conflicted, contained, his face was tense," Lu said.

Lu said Ai was not handcuffed and was wearing his own clothes instead of a detention center uniform. His trademark beard had not been shaven. Lu said the people that arranged the visit, who showed her no identification, made it clear that no questions other than health related ones were allowed.

"We could not talk about the economic charges or other stuff, mainly about the family and health," she said. "We were careful, we knew that the deal could be broken at any moment, so we were careful."

Ai, 53, suffers from high blood pressure and diabetes. He told his wife that he takes long walks everyday, has his blood pressure checked 7 times a day, and that he eats and sleeps very well.

Despite the visit, much about Ai's case remains murky. Family visits are rarely allowed for suspects under criminal investigation until after they are formally charged.

Liu Xiaoyuan, a lawyer and friend of Ai's who met with Lu Monday to discuss the visit, said it sounded like Ai was being held under residential surveillance somewhere outside Beijing.

Chinese law allows police to impose residential surveillance for up to six months before requiring them to make a decision about how to proceed with a case, as opposed to 30 days under criminal detention, said Joshua Rosenzweig, a Hong Kong-based research manager for the U.S. human rights group Dui Hua Foundation.

Such surveillance usually takes place at the suspect's home and is "supposed to be a less restrictive measure than detention," Rosenzweig said in an email. "Instead, the police seem to be using residential surveillance as a way to legitimize extended, incommunicado detention outside of a regular detention facility."

Ai's elder sister Gao Ge said that her family is relieved to know that Ai is well, but hopes the government can clarify what is going on with his case.

U.S. Secretary of State Hillary Rodham Clinton and officials from the European Union and elsewhere have called on China to release Ai and criticized Beijing for what they say is backsliding on human rights.

Ai's influence has ranged far beyond that of the usual contemporary artist. His outrage at the deaths of so many students in the Sichuan earthquake in 2008 turned him into a social activist and tapped into anger among many Chinese at official corruption and indifference. He took to Twitter, prolifically tweeting not only his social criticism but his everyday doings, attracting more than 70,000 followers, even though Twitter is blocked by China's Internet filtering.

Since his disappearance, art museums such as the Tate in London, collectors and artists have rallied behind him. At the launch of an exhibition of Ai's sculpture earlier this month, New York Mayor Michael Bloomberg said fearlessness in the face of official intimidation spoke to "the indomitable desire for freedom that is inside every human being."