Congressional Democrats took their first step Thursday to investigate the Trump administration for firing Attorney General Jeff Sessions, something they fear will herald the suppression of special counsel Robert Mueller’s investigation of President Trump’s ties to Russia.

The likely incoming House Democratic chairs of the intelligence, judiciary, oversight committees, joined by Senate Judiciary ranking Democrat Dianne Feinstein, formally requested the preservation of “all documents, records, memoranda, correspondence and other communication” relevant to “the work of the Office of the Special Counsel” or Sessions’ Wednesday afternoon firing.

Reps. Adam Schiff, Jerrold Nadler, Elijah Cummings, and Sen. Feinstein sent letters requesting the document preservation to the White House counsel, the new acting attorney general Matt Whitaker, FBI director Christopher Wray, U.S. attorney for the southern district of New York Robert Khuzami. Less obviously, they sent the same request to Treasury Secretary Steve Mnuchin, CIA Director Gina Haspel, Director of National Intelligence Dan Coats, IRS Commissioner Charles Rettig and National Security Agency Director Paul Nakasone.

“We remind you that concealing, removing or destroying such documents may constitute a crime,” the Democrats wrote to the various Trump administration recipients.

—Spencer Ackerman