China's most famous artist is under investigation for suspected "economic crimes."

Ai Weiwei was arrested by authorities Sunday just before he boarded a flight to Hong Kong.

Ai designed the bird's nest Olympic Stadium for the 2008 Summer Games. He's been an outspoken government critic.

Police aren't commenting on his arrest but the government often uses the catch-all charge of economic crimes to discredit and detain those who speak out on human rights and free speech.

The U.S. government, along with human rights groups, are calling for Ai's immediate release.