Facebook CEO Mark Zuckerberg and Google CEO Sundar Pichai signaled they are open to testifying to Congress as part of lawmakers’ ongoing antitrust probe into the tech industry, while Apple has not yet explicitly agreed to send its leader.

The companies’ commitments came in letters sent this weekend to the House Judiciary Committee, which has been investigating big tech since last year, according to two people familiar with the matter who spoke on condition of anonymity to discuss an investigation.

If lawmakers proceed as planned, the hearing could represent the most high-profile, public grilling of the tech industry’s most powerful chief executives, a made-for-television moment that comes as federal agencies continue to probe whether Apple, Amazon, Facebook and Google threaten competition, and in the process, harm corporate rivals and consumers.

Facebook and Google declined to comment, while Apple did not respond to requests. A spokesman for Rep. David Cicilline (D-R.I.), who chairs the House’s top antitrust panel, did not immediately respond to a request for comment.

In letters to committee leaders, Facebook and Google signaled they would dispatch their top executives as long as other tech giants’ leaders participate, the sources said. Amazon chief executive Jeff Bezos also has signaled he will participate in the hearing, after the e-commerce giant initially resisted lawmakers’ demands, The Post reported this week. Bezos owns The Washington Post.

Apple, meanwhile, told the committee that it would send a senior executive yet did not clearly commit its leader, Tim Cook, to appearing before lawmakers, according to one of the people with knowledge of the matter. That approach could ratchet up tensions between the iPhone giant and lawmakers in Washington, who previously had threatened to issue a subpoena forcing Bezos to appear before Amazon ultimately expressed an openness to it.

House Democrats and Republicans embarked on their antitrust probe last year, hoping to scrutinize Silicon Valley’s business practices -- and determine if federal competition laws properly have kept pace. Cicilline, the leader of the inquiry, has said he aims to produce a report on the matter this year, and the document is expected to recommend new regulation or other action against Apple, Amazon, Facebook and Google.

To form its conclusions, House leaders have requested an exhaustive list of documents from the four tech companies, seeking to study everything from their past acquisitions to their executives private communications. In the meantime, lawmakers have given a public stage to news media groups, tech startups and other businesses that claim their endeavors have suffered at the hands of big tech.

The congressional inquiry complements a slew of additional investigations under way at the Department of Justice and the Federal Trade Commission. DOJ leaders are expected to file an antitrust case against Google this summer, with a similar lawsuit to follow from state attorneys general who are also probing the search-and-advertising giant.