But it turned out the cause of the blockages was a change made by Google that triggered the Great Firewall to mistake it for another site that is currently being blocked.
Google released a statement later on Tuesday saying that a tweak it made to its search parameters inserted a code string inside search URLs that resembled the URL for Radio Free Asia, a Web site typically blocked by the Great Firewall. The statement follows below in its entirety:
"Lots of users in China have been unable to search on Google.com.hk today. This blockage seems to have been triggered by a change on Google's part. In the last 24 hours "gs_rfai" started appearing in the URLs of Google searches globally as part of a search parameter, a string of characters that sends information about the query to Google so we can return the best result. Because this parameter contained the letters rfa the great firewall was associating these searches with Radio Free Asia, a service that has been inaccessible in China for a long time--hence the blockage. We are currently looking at how to resolve this issue."
For more on this story, read Google search tweak takes Chinese search offline on CNET News.