The Justice Department warned on Wednesday that leading technology companies may be “intentionally stifling the free exchange of ideas” and hurting competition, an ominous development for an industry already under fire from Capitol Hill, President Trump and a range of conservative critics.

The two-sentence statement, which didn’t elaborate on the allegation or explicitly threaten legal action, echoed tweets by Trump last week claiming that the technology industry was biased against conservatives. The White House later threatened new regulation of the search giant Google, which legal experts said would violate constitutional protections on free speech.

The Justice Department made its announcement at the conclusion of a Senate hearing in which Facebook and Twitter executives faced sharp questioning on a number of subjects — including allegations that social media platforms mute conservative voices. Google offered to send an executive to the hearing, but the Senate committee rebuffed him because it wanted the chief executive of Google’s parent company, Alphabet, to appear.

The combination of government action, including a coming meeting between Attorney General Jeff Sessions and several attorneys general, alarmed the technology industry. It has been playing defense for nearly two years over allegations that it failed to adequately combat the spread of phony news reports and Russian disinformation during the 2016 presidential election.

Outside legal experts, meanwhile, expressed concern that the rising political pressure over unproven allegations of bias will end up chilling constitutionally protected speech by technology companies.

“This could be a very serious broadside against the entire Internet industry coordinated by multiple layers of government,” said Eric Goldman, co-director of the High Tech Law Institute at Santa Clara University, in Silicon Valley.

The meeting with state attorneys general will “discuss a growing concern that these companies may be hurting competition and intentionally stifling the free exchange of ideas on their platforms,” according to the Justice Department statement.

It noted that government lawyers had been listening to the Senate Intelligence Committee hearing “closely,” though issues of bias played a relatively small role in the hearing. The subject was the focus of a later one, Wednesday afternoon, before the House Energy & Commerce Committee with only Twitter.

The Sessions meeting with the state attorneys general, which was planned before Wednesday’s Senate hearing but not previously announced, is tentatively scheduled for Sept. 25 in Washington, according to a person familiar with the plans who was not authorized to speak publicly. Justice Department officials declined to specify which states would be represented, but the attorneys general in several states have opened investigations into technology companies in the past two years on various issues.

Sessions regularly faces withering public criticism from Trump, but he has also been one of the president’s most loyal supporters, particularly on policy matters such as immigration and policing. Sessions’s statement Wednesday on social media firms marks another instance in which he has echoed points raised earlier by the president.

Google, Twitter and Facebook all declined to comment in response to the Justice Department statement. All three have repeatedly denied allowing political views to shape what content appears on their platforms.

Twitter Chief Executive Jack Dorsey said in the Senate Intelligence Committee hearing Wednesday morning, “Impartiality is our guiding principle.”

In written testimony submitted ahead of the hearing, he cited a study by the company that concluded that tweets by Democratic and Republican lawmakers have equal reach.

Technology companies have, since 2016, been more aggressive in policing hate speech, fake accounts and disinformation campaigns by foreign governments. The removal of conservative conspiracy theorist Alex Jones from several social media platforms last month has fueled claims that the companies are targeting conservative voices, though he was removed for violating rules against hateful speech — not for the political bent of his posts — according to the companies.

The industry’s conservative critics have not presented systematic evidence to bolster their claims.

Legal experts called the Justice Department’s statement on Wednesday unusual and a potential threat to the First Amendment rights of technology companies, which may alter their behavior because of the implicit threat of action by federal and state investigators.

“It’s not clear what they’re investigating. If they’re investigating companies without a clear reason, it’s possible that the investigations themselves will stifle free speech,” said Alex Abdo, a senior staff attorney at the Knight First Amendment Institute at Columbia University. “DOJ without some clear implication of wrongdoing, should not be meddling.”

The combination of legal theories put forward by the Justice Department statement also puzzled legal experts.

They said that there are legitimate issues regarding the market power of leading technology companies that may merit more government review, particularly with regard to situations in which companies are using their power in one marketplace — such as Internet search — to gain advantage in another, such as retail. The European Union has investigated such issues and, in July, hit Google with a $5 billion fine for bundling apps on its Android mobile operating system in a way that undermined competition.

But legal experts say the First Amendment protects against the government directing tech companies in the dissemination of news or political opinions. They said Justice Department lawyers would struggle to mount a case that sought to limit such free speech rights.

“They’re just throwing a bunch of stuff at the wall to see if it sticks,” said Heather Whitney, a doctoral candidate at New York University who wrote an influential paper this year on free speech and technology companies. A spokesman for the DOJ declined to comment.

The Justice Department’s statement came after months of threats from the president to regulate or investigate the country’s technology companies over allegations of bias. In July, he accused Twitter of intentionally hiding top Republican users’ tweets, pledging to “look into this discriminatory and illegal practice” without providing further details.

Then, last month, Trump claimed that Google rigged search results before one of his top advisers suggested that the White House could soon consider new regulations. The president later appeared to backtrack from the idea.

By last week, though, Trump told Bloomberg News that technology companies including Amazon.com and Facebook are in a “very antitrust situation,” though he said he wasn’t looking to break them up. He also aired these complaints at a rally in Evansville, Ind., telling supporters: “I’ve made it clear that we as a country cannot tolerate political censorship, blacklisting and rigged search results.”

Earlier Wednesday, Democrats and Republicans on Capitol Hill focused their attention on other issues — including key questions as to whether Facebook, Twitter and its tech peers have hardened themselves against disinformation spread by foreign powers ahead of the 2018 elections.

Both Sheryl Sandberg, the chief operating officer of Facebook, and Jack Dorsey, the chief executive of Twitter, defended their companies’ work after Russian agents reached million of Americans with divisive political messages during the presidential race just two years earlier.

“We were too slow to spot this and too slow to act. That’s on us,” Sandberg told the Senate Intelligence Committee. “This interference was completely unacceptable. It violated the values of our company and of the country we love.”

Among those attending the hearing was Jones, who hurled insults at Sen. Marco Rubio (R-Fla.) and then verbally attacked a CNN reporter in the hallway — a barrage of taunts he live-streamed. He ceased minutes before House lawmakers convened a testy hearing on allegations of anti-conservative bias, where Dorsey, the session’s lone witness, sought to stress the company’s political neutrality.

“Humans are building the algorithms. Humans make decisions about Twitter’s terms of services ... and humans can make mistakes,” said Rep. Greg Walden (R-Ore.), the chairman of the House Energy and Commerce Committee, to open the hearing.

But Democrats sharply rebuked Republicans, including the president, for airing allegations of conservative bias without presenting evidence. Rep. Frank Pallone Jr., the top Democratic lawmaker on the panel, described the hearing as “one more mechanism to raise money and generate outrage” on the part of Republicans.

“It appears Republicans are desperately trying to rally their base by fabricating a problem that simply doesn’t exist,” Pallone said.