The top law enforcement officers in several states are gearing up to launch an antitrust investigation of Silicon Valley’s biggest firms, according to multiple reports, adding to the scrutiny tech companies are already facing from federal regulators.

The investigation is expected to get off the ground as soon as next month and would follow a meeting representatives from states had with antitrust officials from the Justice Department last month.

A group of state attorneys general plan to soon issue civil investigative demands to the tech companies, and the investigation will examine whether Silicon Valley’s most powerful firms suppressed competition in the tech industry.

It’s unclear how many states are expected to participate and whether it will be a bipartisan group, but the Wall Street Journal reported as many as 20 attorneys general could join the effort.

After last month’s meeting at the Justice Department, the office of Texas Attorney General Ken Paxton, a Republican, said a group of eight state attorneys general met with Attorney General William Barr to discuss “the real concerns consumers across the country have with big tech companies stifling competition on the internet.”

Paxton’s office said the states are “considering a range of possible antitrust actions against such companies.”

An investigation into big tech companies spearheaded by the states would run alongside investigations launched by the Justice Department and Federal Trade Commission into anticompetitive behavior by leading internet companies.

The Justice Department said last month it had opened a sweeping antitrust review into “market-leading online platforms,” which is likely to include Amazon, Facebook, and Google. The Federal Trade Commission launched a technology task force in February designed to monitor competition in the tech sector and investigate any possible anticompetitive conduct.

The commission also opened an antitrust investigation into Facebook, the social media company acknowledged in financial filings last month.

The inquiries from the federal government come alongside continued efforts in Congress to examine the practices of some of the country’s biggest technology companies.

To address the growing dominance of Silicon Valley firms and whether they have shut smaller competitors out of the marketplace, 2020 Democratic presidential contender Elizabeth Warren called for breaking up the Facebook, Amazon, and Google, while Sen. Ted Cruz, R-Texas, has proposed antitrust action against big tech companies.