Controversial artist Ai Weiwei

Hundreds of people visited the Shanghai studio of controversial artist Ai Weiwei Sunday for a "River Crab Feast" and a last chance to see the structure before it is demolished by local authorities.

Zi Xiangdong, press officer at the Beijing Municipal Public Security Bureau, refused to comment on the issue. "Police will not release information about sensitive people," Zi told the Global Times Sunday.

"More than 500 people visited the studio Sunday. Most participants are Internet users who came on their own," Xie Zhengwei, a worker at the studio, told the Global Times Sunday.

Ai had planned the party as a farewell to the 2,000-square-meter studio, which received a government notice last week ordering its demolition.

Authorities in Shanghai said the structure had not gone through the proper application procedures.

"Ai's studio did not go through the application procedures, therefore, it is an illegal building," Chen Jie, director of the urban construction department in Malu township, the home of the studio, said earlier.

Ai claimed it was the head of Shanghai's Jiading district, Sun Jiwei, who had asked him to build the studio two years ago.

Overseas media reported that Ai was stopped by Beijing police at the airport as he was about to depart for Shanghai, then put under house arrest.

Ai told the Global Times that the house arrest lasted until midnight Sunday.

Zhou Shuguang, 29, traveled from his home in Changsha, Hunan Province to visit the studio Sunday.

"Although I heard that Ai was under house arrest, I wasn't scared because as a visitor, I just come to the party to have fun by myself. We are not being investigated by anyone. I don't believe the police will detain us," he said.

Visitors to the studio have been taking pictures since Sunday morning.

Each participant was served with a river crab, and also received two ceramic sunflower seeds, replicas of the hundred million ceramic sunflower seeds currently on exhibition at the Tate Modern's Turbine Hall in the UK. One visitor, 39, who refused to give his name, said that the party was a good chance for Internet users to meet up and make friends.

Participants said no police were present at the studio.