A look at the key players, witnesses in Trump-Russia probe

The House Intelligence Committee is set to hear testimony from multiple witnesses as the body probes Russia's 2016 election involvement in a closed hearing this week.

The allegations surrounding possible ties between the Russian state and Trump's 2016 campaign have swirled since the president's historic upset victory over Democratic candidate Hillary Clinton. After assuming the presidency, the actions of people past and present within Trump's inner circle have been called into question on both a formal and informal scale.

Get to know the key players within Trump's inner circle who have been accused of having ties to Russia:

Informally, narratives have been outlined, politicians have sounded off -- including Democratic Rep. Maxine Waters, who said on the allegations that President Trump is "leading himself to impeachment" -- and polls continue to show American concern around Trump's alleged Russia ties. But many allegations remain unproven.

Formally, both FBI Director James Comey, the House Intelligence Committee and the Senate Select Committee on Intelligence have announced they are respectively investigating these allegations. It was reported last week that the House Intel Committee's witness list includes somewhere between 36 and 48 people.

Former Trump campaign manager Paul Manafort, former national security adviser Michael Flynn and Carter Page have each been individually linked to the Trump-Russia allegations, and will likely make appearances at the closed Committee hearings.

Manafort recently agreed to testify, while Page volunteered himself to do so.