There is a major force uniting America’s fiercely partisan politicians: big technology companies. Democrats and Republicans at the federal and state levels are coming together to scrutinize the power of the Silicon Valley giants and, potentially, to rein them in.

Letitia James, the Democratic attorney general of New York, announced on Friday that attorneys general in eight states — four Democrats and four Republicans — and the District of Columbia had begun an antitrust investigation of Facebook.

Next up for state regulators is Google. A similarly bipartisan group led by eight attorneys general is set to announce on Monday a separate but comparable investigation. The search giant is expected to be the focus of the inquiry, according to two people familiar with the plan, who spoke on the condition of anonymity before the official announcement. Attorney General Ken Paxton of Texas, a Republican, is taking a leading role in the Google investigation, the people said.

The state inquiries coincide with bipartisan scrutiny of the tech giants in Washington, by House and Senate committees, the Justice Department and the Federal Trade Commission. Federal officials are examining the practices of Amazon and Apple as well as those of Facebook and Google.