The Senate Intelligence Committee, which is investigating Russian interference in the presidential race, has asked President Donald Trump’s political organization to gather all documents, e-mails and phone records going back to his campaign’s launch in June 2015, two people briefed on the request said.

The letter from the committee arrived at Trump’s campaign committee last week and was addressed to the group’s treasurer. Since then, some former staffers have been notified and asked to cooperate, the people said. They were not authorized to speak publicly.

Dozens of former staffers are expected to be contacted in the coming days to make sure they are aware of the request, the people added.

The letter was signed by Sen. Richard Burr, R-N.C., the Senate committee’s chairman, and Sen. Mark Warner, D-Va., the committee’s ranking Democrat.

The request to Trump’s political operatives represents the first time that Trump’s official campaign structure has been drawn into the Senate committee’s ongoing bipartisan investigation. That investigation is separate from the federal probe being led by the Justice Department’s special counsel, former FBI director Robert Mueller.

In recent months, several Trump campaign associates have been contacted by Senate investigators, but the campaign itself had not been asked to preserve materials.

Trump’s campaign committee is now led by former deputy campaign manager Michael Glassner and John Pence, a nephew of Vice President Mike Pence.