Google CEO Sundar Pichai takes the stage during the presentation of new Google hardware in San Francisco on Oct. 4, 2016.

The Missouri attorney general's office is investigating whether Google has run afoul of consumer protection or antitrust laws in the state.

Attorney General Josh Hawley's office said on Monday that it issued a subpoena to investigate if Google's use of information that it collects about consumers is appropriate and if the company stifles competing websites in search results.

Google has largely steered clear of antitrust problems in the U.S. That's not the case in Europe, where the company faces a fine of about $2.7 billion over the display of its shopping ads. Google has challenged the decision in Europe, citing competitors like Amazon and eBay and arguing that its process doesn't favor "ourselves, or any particular site or seller" but rather is "the result of hard work and constant innovation, based on user feedback."

The Federal Trade Commission has come to rely more heavily on states attorneys general for enforcement. The FTC sometimes comments on state regulations or coordinates a joint investigation, and state attorneys general can bring federal antitrust suits on behalf of a citizen of their state.

Google Spokesperson Patrick Lenihan told CNBC that Google has not yet received the subpoena.

"[W]e have strong privacy protections in place for our users and continue to operate in a highly competitive and dynamic environment," Lenihan said.