Google Inc.'s search sites in China abruptly stopped working Tuesday, but the explanation for the outage shifted as the day wore on. The Internet giant first blamed itself, citing a technical change, but later reversed course and pointed to the heavy hand of China's "Great Firewall"—even as service appeared to be back to normal.

The evolving explanation whipsawed Google watchers and showed how fraught with confusion the relationship between China and Google remains. The episode risks escalating their battle a week after Google...