Internet users in Beijing and Shanghai said attempts to access Google and other search engines were successful Friday, despite claims on a U.S. blog that traffic to these sites was redirected to Chinese search engine Baidu.com.

The claim first surfaced on TechCrunch, a U.S. blog that largely covers Internet start-ups before being picked up by other sites. The headline of that post alleged "Baidu hijacking Google traffic In China," but offered no evidence to prove the claim apart from an undated, modified screenshot showing Baidu's Web page below the URL for Google Blogsearch.

In a follow-up post, TechCrunch said "new reports have surfaced that would indicate that China has unilaterally blocked all three major search engines in China and is redirecting all requests to Baidu." That report cited posts on other blogs, where users claimed to have been redirected from U.S. search sites to Baidu.

A Google spokeswoman in Beijing did not immediately respond to an e-mail seeking comment.

However, several Internet users -- four in Beijing and two in Shanghai -- reported on Friday morning that search engines operated by Google, Yahoo and Microsoft, including Google Blogsearch, one of the sites reportedly most affected, were accessible. Attempts to reach these sites had not been redirected to Baidu, they said.

Internet censorship is a serious problem in China, and regulators routinely block access to sites with content they don't like. But Chinese officials very rarely comment on censorship efforts, making it difficult for users to determine when a site has been blocked or is inaccessible for other reasons.

Timing can be an important factor, with Chinese censors blocking access to some Web sites around politically sensitive dates, such as the June 4 anniversary of the 1989 Tiananmen massacre and the Chinese Communist Party Congress, a political confab held once every five years to choose top leaders and set policy that is now underway in Beijing.

Access to a search engine can also be blocked if a user searches for a politically sensitive word, such as a search for information on the banned Falungong religious sect.

Tracking the ebb and flow of censorship efforts can be a challenge, as access to sites can be blocked and opened, seemingly by whim. On Wednesday, Wikipedia remained blocked in China and access to YouTube was shut off. But censors eased off on other sites, opening up access to Google's Blogspot blogging service and permitting users to view pictures on Flickr, which had been blocked even though the site was accessible in China.

The IDG News Service is a Network World affiliate.