Attorney General William P. Barr has tapped the U.S. Attorney in Connecticut to examine the origins of the Russian election-interference probe, according to reports late Monday.

John H. Durham, the top federal prosecutor in Connecticut, has been asked get the bottom of the Justice Department’s investigation into members of the Trump presidential campaign.

Mr. Durham’s probe will focus on whether the Justice Department lawfully collected intelligence on Trump campaign associates, according to both the New York Times and Associated Press, each citing sources familiar with the matter.

Durham has a history of serving as a special prosecutor investigating potential wrongdoing among national security officials, including the F.B.I.’s ties to a crime boss in Boston and accusations of C.I.A. abuses of detainees.

President Trump has long demanded the Justice Department look into whether the FBI spied on his campaign at the behest of the Obama administration.

Mr. Durham’s probe is the third known investigation into FBI and Justice Department decisions surrounding the 2016 election.

Justice Department Inspector General Michael Horowitz is evaluating the Justice Department’s wiretaps on former campaign associate Carter Page.

And John Huber, the U.S. attorney in Utah, is also reviewing a surveillance warrant obtained by the FBI to spy on Mr. Page.