WASHINGTON — White House lawyers have instructed the president’s aides to preserve materials that could be connected to Russian interference in the 2016 election and other related investigations, three administration officials said Wednesday.

The instructions, which were sent to White House staff on Tuesday, come after Senate Democrats last week asked the White House and law enforcement agencies to keep all materials involving contacts that Trump’s administration, campaign and transition team — or anyone acting on their behalf — have had with Russian government officials or their associates.

The Senate intelligence committee, which is investigating Russia’s role in the 2016 election, has also asked more than a dozen organizations, agencies and individuals to preserve relevant records.

The three administration officials who confirmed that White House staffers were instructed to comply did so on the condition of anonymity because they were not authorized to publicly disclose the memo from White House counsel Don McGahn.

President Donald Trump has been dogged by questions about his advisers’ ties to Russia since the campaign. Federal investigators have been looking into possible contacts between Trump advisers and Russia, while congressional committees are investigating Russia’s role in political hacking during the campaign.

The intelligence community has assessed that Russia’s hacking of Democratic groups and operatives was carried out to help Trump defeat Democrat Hillary Clinton.