After several states began pursuing an antitrust probe of the big technology companies, sources reported that representatives of several state attorneys general met with top Justice Department officials to air their concerns about the lack of competition in the technology sector. Now, according to sources, a bipartisan group of states plans to initiate a joint antitrust investigation, to be launched as soon as next month. Sources say the investigation will focus on whether dominant platforms stifle competition.

The New York Times reports that sources revealed that, “as part of the probe, the states are likely to issue civil investigative demands, similar to subpoenas, to tech companies and other businesses.”

The number of states that might take part in the investigation wasn’t revealed, but a source said it could be up to 20. The states’ investigations “could dovetail” with the Justice Department’s antitrust review that, said sources, will focus on Google and Facebook. Amazon, Apple, Facebook and Google are “likely to be a focus of the new investigation.”

NYT ascertained that North Carolina attorney general Josh Stein, a Democrat is “participating in bipartisan conversations about this issue.” Mississippi attorney general Jim Hood, another Democrat, said he is still “concerned with the aggregation of data in the hands of a few and [I] am always watchful of any monopoly,” and Texas attorney general Ken Paxton, a Republican, said that he and other state attorneys general discussed “the real concerns consumers across the country have with big tech companies stifling competition on the Internet.”

As the Justice Department and the Federal Trade Commission investigate antitrust concerns, “the involvement of state attorneys general could add to complexity and cost for the companies.” This larger group was “a driving force in the landmark joint state-federal antitrust case against Microsoft two decades ago … but the states eventually splintered over whether to accept a settlement.” But, noted the experts, the states’ involvement “expanded and extended the legal battle, at times significantly.”

Representatives from the four tech companies in the crosshairs referred to experts who stated that they had “helped reduce prices and expand choice for consumers and merchants in the U.S. and around the world … [while they face] intense competition for all of the products and services that we provide.” Legislators and legal experts, however, “worry that significant slices of the high-tech marketplace have become uncompetitive … [including] advertising, search, social media, app sales and certain retail sectors, among others.”