Texas' attorney general, firing its latest salvo in a two-year investigation of Google's search rankings, demanded that the Internet company cooperate with its probe and hand over intentionally withheld documents.

In a court filing, the state's attorney general said Google was holding out despite having handed over hundreds of thousands of documents since August 2010.

The attorney general's office "suspects that there are many documents being improperly withheld based on assertions of privilege," according to the filing. "Google has significantly over-reached in its effort to prevent disclosure of documents."

The intensifying inquiries around the globe into Google's business practices recall the fervor with which regulators went after Microsoft earlier last decade.

The Lone Star state's probe is just one of several spearheaded by federal regulators, foreign governments and individual US states, all seeking clarity on how the Internet search leader ranks its search results.

In Europe, regulators are likely to release key rulings soon in an EU investigation that began in 2010, in a case that marks a coming-of-age for the Internet giant whose once oft-quoted mantra was "Don't Be Evil".

Google's rivals accuse the company of favoring its own content and properties.

Google, which accounts for an estimated two-thirds or more of searches conducted on the Internet, said it was cooperating with the investigation.

"We have shared hundreds of thousands of documents with the Texas Attorney General, and we are happy to answer any questions that regulators have about our business," Google said in a statement.

The company has argued that, while it dominates search, it's now fending off increasingly powerful competition from the likes of Apple and Facebook in a range of markets.

And despite being increasingly in the crosshairs of antitrust investigations, Google has been reluctant to share its methodology on search rankings, arguing that the algorithms behind its search engine is a valuable business secret.

But fighting the probes may also come at a steep cost. The European Commission could fine Google up to 10 percent of global revenues - nearly US$40 billion last year - and order changes to its operations. The alternative, a long battle in EU courts, might harm its image, analysts say.

- Reuters