A Senate panel voted Thursday to subpoena the top executives of Facebook, Google and Twitter to answer questions on disinformation, online scams and a range of social ills.
The Commerce Committee agreed unanimously to call Jack Dorsey of Twitter, Mark Zuckerberg of Facebook and Sundar Pichai of Google parent Alphabet.
The move comes with Big Tech platforms facing heightened scrutiny on monopoly concerns, and also for failing to stem hateful and nefarious content.
"After extending an invitation to these executives, I regret that they have again declined to participate and answer questions on the record about issues that are so visible and urgent to the American people," said Republican Senator Roger Wicker, who chairs the panel.
"We have questioned how they are protecting and securing the data of millions of Americans, we've explored how they're combating disinformation fraud and other online scams, we've examined whether they are providing a safe and secure internet experience for children and teens."
Wicker added that the panel wants to know "how they are removing content from their sites that encourages extremism and mass violence... their use of secret algorithms that may manipulate users and drive compulsive usage of the internet, among our youth."
Big Tech firms, including Amazon, Apple and Microsoft, have seen their economic power grow in recent years and accelerate during the coronavirus pandemic, dominating a range of economic sectors.
President Donald Trump and his allies have claimed tech platforms are biased against conservatives, despite his own vast social media following.
Democrats meanwhile have expressed concerns over monopoly abuses and the failure of social media to stem misinformation from Trump himself.
Lawmakers from both parties have called for changes to the legal liability shield of online services under a law known as Section 230, claiming the provision enables toxic and harmful content to proliferate.
Google and Facebook are also under scrutiny by federal and state antitrust regulators.