Announced from the steps of the Supreme Court Monday afternoon, the probe by the states is intending to focus on what it refers to as Google's "online search juggernaut", and the ways in which its bid for ad revenue dominance may have impacted the quality of searches themselves.
"Google monitors our online behavior, and captures data on every one of us as we navigate the Internet", Attorney General Ashley Moody, a Republic from Florida, said in a statement. Tara Gallegos, a spokeswoman for California Attorney General Xavier Becerra, declined to confirm or deny any state investigation and would not comment on the announcement by the other states.
"We intend to closely follow the facts we discover in this case and proceed as necessary", he added.
The U.S. Justice Department opened a sweeping investigation of big tech companies this summer, looking at whether their online platforms have hurt competition, suppressed innovation or otherwise harmed consumers.
As more facts become known, the investigation may expand its scope to emerging areas where Google "is unfairly exerting its influence", according to the release.
The probe is being backed by 48 states - with only California and Alabama absent - and joined by Puerto Rico and the federal District of Columbia, and officials stopped short of calling for any specific remedies such as a breakup - which some Google critics have called for.
"There's nothing wrong with being a dominant player when it's done fairly", said Sean Reyes, the Republican attorney general of Utah.
The investigation is the latest in a long series of high-profile probes into the way the company conducts its business, which has often come under the scanner of public regulators and anti-monopoly activists, not to mention various privacy watchdogs from around the world.
Sen. Josh Hawley (R-MO), who is one of the leading voices taking on big tech in the Senate, tweeted: "It's going to be a very bad day for @google".
Indiana Attorney General Curtis Hill was among those who spoke at a press conference in Washington.
The latest investigation includes almost all 50 USA states, except for California and Alabama. Google's dominance in online search and advertising enables it to target millions of consumers for their personal data. In a blog post published by Google last week, the company confirmed that the Department of Justice has asked it to provide information about its business practices. Washington is home to two of America's largest tech companies, Amazon and Microsoft.
President Donald Trump's objections with Google are different.
Attorney General Paxton clarified that this investigation is not a lawsuit but a probe to determine the facts.