China silent as activist artist Ai Weiwei's vanishes post-arrest

Ai Weiwei has become one of China's most outspoken critics, complaining about a lack of human rights. He was detained on Sunday morning while travelling with an assistant, Jennifer Ng.

According to Ng, Ai Weiwei was taken away by border guards, the BBC reports. Since then one has seen or heard from him since. The authorities have not commented in his regard.

"I went back to check with the security officers and they said, 'He has other business - you go on the flight on your own'," she said.

A few hours later, more than 40 police officers raided the artist's Beijing studio, the BBC also reports.

Dozens of items were confiscated, said another assistant, and several people were taken to a nearby police station. They were released a few hours later.

Weiwei helped design the main stadium used in the Beijing Olympic Games in 2008. It became known as the Bird's Nest because of its intricate steel latticework.

He currently has an exhibition at the Tate Modern gallery in London. It is made up of 100 million porcelain objects made to look like sunflower seeds, a popular snack food in China.

The artist has also become a vocal critic of the Chinese government.

Some of his work has political connotations - he tried to gather the names of every school child who died during the Sichuan earthquake in 2008 in one instance. The quake is a sensitive subject as many schools colapsed in the earthquake, leading to claims that they were shoddily built.

The Chinese government is reluctant to talk about this issue and has arrested activists who do. Weiwei was also known to lend his support to others who have tackled the authorities.