Sen. Mark Warner (D-Virginia), incoming chair of the Senate Intelligence Committee, is asking mobile carriers and social media platforms to preserve “content and associated metadata” that may be connected to the attack on the US Capitol. Warner said in a statement Saturday that he contacted the CEOs of AT&T, T-Mobile, Verizon, Apple, Facebook, Gab, Google, Parler, Signal, Telegram, and Twitter.

“The United States Capitol is now a crime scene,” Warner wrote in his letters. “The FBI and other law enforcement agencies are currently investigating the events of that day, and trying to piece together what happened and the perpetrators involved. The prospect of litigation on behalf of the victims of the mayhem also is highly likely. Messaging data to and from your subscribers that may have participated in, or assisted, those engaged in this insurrection – and associated subscriber information – are critical evidence in helping to bring these rioters to justice.”

Warner noted that many of those participating in the January 6th attack that left five people dead posted images to social media, or shared them via text and mobile messaging platforms while the riot was underway and afterward, “to celebrate their disdain for our democratic process.”

All the named companies routinely comply with court-issued preservation orders, issued during criminal investigations. But Warner’s letter is an informal request, without the legal force of a criminal preservation order, and it is unclear how the companies will respond. Court-issued preservation orders are often issued under seal so it is also possible that one of the many agencies investigating the Capitol raid has already issued such an order.

We’ve reached out to the companies to ask how and if they plan to comply with Warner’s request and will update if we hear back from them. A Facebook spokesperson said in an email to The Verge that the company was “continuing our ongoing, proactive outreach to law enforcement and have worked to quickly provide responses to valid legal requests. We are removing content, disabling accounts, and working with law enforcement to protect against direct threats to public safety.”

Warner told Politico that following Wednesday’s attack, Congress would “come back with a vengeance” against social media platforms that were unable to rein in violent content and threats on their platforms. “This is going to come back and bite ‘em,” he said.

Update January 9th 1:15PM ET: Adds comment from Facebook