Google, which is based in Mountain View, Calif., decided to stop censoring its search results in China in 2010. To avoid breaking the country's laws, Google moved the computers for its Chinese search engine from the country's mainland to Hong Kong, where the same censorship requirements aren't imposed.
Since Google took its stand against censorship, its search engine and other services have been periodically unavailable.
YouTube, Google's popular video site, has been blocked in China since 2009, according to the company.
Associated Press writer Didi Tang in Beijing contributed to this report.