Attorney General Josh Hawley of the state of Missouri issued an investigative subpoena to determine whether the company's actions violated state antitrust and consumer protection laws. He says the company will be held accountable and Missouri is not giving Google a free pass.
He said, however, that Google has "strong privacy protections in place for our users" and that it continues "to operate in a highly competitive and dynamic environment".
Google, a unit of Alphabet Inc., didn't immediately respond to a request for comment.
"When a company has access to as much consumer information as Google does, it's my duty to ensure they are using it appropriately", Hawley said in the statement.
"This misappropriation hurts business and it threatens to drive Google's competitors out of the market, which in turn deprives consumers of innovation and valuable services", he says.
Federal regulators in the USA have also investigated Google over antitrust claims. He says "substantial evidence" suggests the company might manipulate search results to list Google-affiliated websites higher in search results.
Also of interest to Hawley's investigation is the roughly 70 percent of all card transaction information that Google collects.
Hawley on Monday announced the investigation, which comes on the heels of a $2.7 billion fine issued to the company by the European Union for antitrust violations.