The attorney general's office has asked Google for information regarding Foundem, SourceTool/TradeComet and myTriggers, each of which have complained in the past that Google pushed them down its search rankings or reduced their appeal to advertisers.

As it did during the initiation of the European Commission antitrust investigation, Google on Friday highlighted connections between the complainants and Microsoft. Foundem, Google notes, is backed by the Initiative for Competitive Online Marketplace, an organization funded in part by Microsoft. MyTriggers and SourceTool/TradeComment are represented by Microsoft antitrust attorneys, Google said.

that antitrust complaints usually do come from competitors.

In a blog post, . "Given that not every website can be at the top of the results, or even appear on the first page of our results, it's unsurprising that some less relevant, lower quality websites will be unhappy with their ranking," wrote Don Harrison, deputy general counsel at Google.

Google is cooperating with the Texas Attorney General's Office, he said.