Google Inc blamed the great firewall of China for blocking its Internet search service in the country on Tuesday, but said it did not know if the stoppage was a Chinese technical glitch or a deliberate move in their face-off over Internet censorship.

Whichever it was, the incident underscored the vulnerability of Google's business in the world's largest country.

Google said search traffic in China now appeared to be back to normal following its confirmation earlier on Tuesday of reports that many users in China were unable to search on its Hong Kong-based website.

In an unusual development, however, Google provided a new statement about the disruptions to its search service that reversed the explanation it had offered just three hours earlier.

Google said in an updated statement on Tuesday that changes it made to its search code, which it had initially cited as the cause of blocked searches in China, had been made a week ago, and not in the past 24 hours, as Google had first said.

So whatever happened today to block Google.com.hk must have been as a result of a change in the great firewall, Google said in an emailed statement, referring to China's technology for filtering Internet content.

Asked if the change was a glitch or deliberate, a Google spokeswoman replied: We don't know.

The news comes with Google's Chinese search service already in the headlines due to a censorship dispute with Beijing.

The company shut its mainland Chinese portal Google.cn last week and rerouted searches to its Hong Kong site in order to offer uncensored search results.

Analysts and China experts have been on the lookout for signs that Beijing might clamp down on Google and restrict its services, following harsh official comments in reaction to Google's new approach to offering Internet search in China.

Separately, Google also said its mobile services in China were partly blocked on Sunday and Monday.

Inconsistency in Google's search service to Chinese users could expose a weakness in Google's plan to provide search from Hong Kong, said Pacific Crest Securities analyst Steve Weinstein.

If that continues you'd imagine that they would slowly over time lose share, Weinstein said.

Since Google made the switch last week, sensitive terms like Tiananmen have been blocked by the Chinese government for most mainland Chinese users as was previously the case.

But users in China began on Tuesday to report erratic results on Google.com.hk, saying even searches for non-sensitive terms like hello returned blank pages. At other times, sensitive searches returned a normal result, showing links to pages that are then blocked by China's Internet filters.

Earlier on Tuesday, Google explained the blocking by saying that due to a change on its site, gs_rfai started to appear in the URLs of Google searches globally in the last 24 hours.

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, a Google spokeswoman said in an emailed statement. Google said the problem affected lots of users.

Radio Free Asia is a pro-democracy, pro-human rights media channel that China's censors have blocked.

The updated Google statement said that search traffic to China was now back to normal, even though Google had not made any changes on its end.

We will continue to monitor what is going on, but for the time being this issue seems to be resolved, Google said in the statement.

Google on March 22 said it would pull its Chinese-language search services out of China, citing also a hacking attack late in 2009 that it said originated from the country.

Google -- the world's No. 1 Internet search provider and No. 2 in China behind local search powerhouse Baidu Inc -- has said it intends to retain some business operations in China, including research and development staff and a sales team.

But analysts have said that the Chinese government could make life difficult for Google.

Most investors I talked to were under the impression that any sort of workaround would not be successful, said Needham & Compan analyst Mark May, referring to Google's move to relocate its search service to Hong Kong.

According to Google, its mobile services were partly blocked in China for two days.

On a website showing the accessibility of Google's services in China, the company listed mobile as partially blocked on Sunday and Monday. Prior to Sunday, there were no issues with mobile services in China, according to the site -- http://www.google.com/prc/report.html#hl=en.

Some users in Shanghai on Tuesday reported no problems with searching through Google's mobile service, indicating that the outages are intermittent.

Other mobile users have had problems ever since Google stopped censoring search results in China earlier this month.

A Google spokeswoman would not speculate on the cause for the mobile outages.

Google shares closed $4.26 higher, or 0.8 percent, at $566.71 on Nasdaq. (Reporting by Alexei Oreskovic and Melanie Lee, writing by Lucy Hornby and Tiffany Wu; Editing by Gary Hill)

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