Google has been no stranger to antitrust cases in recent years with the European Commission going after it several times, but there's now mounting pressure in its own country, too. The United States Department of Justice could be about to open legal proceedings against Google, along with numerous state attorneys across the nation and the House Judiciary Committee. Google's home state of California had been reluctant to join but has reportedly opened its own investigation in recent days.

According to Politico, California's Democratic Attorney General Xavier Becerra declined to join the other 48 states (all except Alabama) in their collective investigation into Google's market dominance but has instead sanctioned a separate probe. While the multi-state inquiry focuses on Google's search and advertising business, it's not yet clear what California is specifically looking into.

A federal lawsuit is expected to be filed in the next month or so, and the DOJ has apparently been working closely with individual state attorneys to build its case. To make matters worse, Congress is also scrutinizing Google's practices — Google CEO Sundar Pichai will have to give testimony at a House Judiciary heading along with Apple counterpart Tim Cook, Amazon head Jeff Bezos, and Facebook's Mark Zuckerberg.