The Senate Intelligence Committee sent letters to at least a dozen agencies, individuals and organizations on Friday directing them to preserve records and information related to the committee's investigation of Russian efforts to influence the 2016 election, according to a Senate aide.

Both the House and Senate intelligence committees previously announced investigations focused on Russian interference in the election.

Senate Intelligence Committee Chairman Richard Burr, R-North Carolina, said last week the committee would "aggressively" continue its oversight of possible contact between the Trump campaign and transition teams with Russian government officials.

"We will cast a wide net to look at individuals who can provide us additional insight into what went on," Burr told reporters on Tuesday.

Democrats on the Senate Intelligence Committee also called on the White House, Department of Justice and FBI to preserve documents related to the investigations last week. Democrats asked White House Counsel Don McGahn to confirm that White House and Trump staff are being told to preserve all materials related to contacts with Russia.

It's possible that the committee will call on Gen. Mike Flynn to testify in the investigation. Flynn recently resigned as National Security Adviser after reports surfaced that he discussed sanctions on Russia with the Russian ambassador during the presidential transition and possibly misled Vice President Mike Pence about the nature of that conversation.