The Senate Intelligence Committee, which is investigating Russian interference in the 2016 presidential race, has asked President Trump’s political organization to gather and produce all Russia-related documents, emails and phone records going back to his campaign’s launch in June 2015, according to two people briefed on the request.

The letter from the Senate 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.

The demand follows a Senate request months earlier for the campaign committee to preserve documents.

Dozens of former staffers are expected to be contacted in the coming days to make sure they are aware of what they are required to produce and how to submit those documents, the people added.