Two top Republican senators want the Department of Justice (DOJ) to brief them on its efforts to investigate alleged "spying" during the 2016 election after Attorney Generaltold lawmakers that he was looking into the issue.

Sens.(R-Wis.) and(R-Iowa) — the chairman of the Homeland Security and Finance committees, respectively — sent Barr a letter on Thursday pressing him for details on his review.

"We share your concerns about these activities, and are troubled by the apparent unauthorized disclosures of surveillance efforts and other classified information during the same time period," the two senators wrote in their letter

The letter comes after Barr sparked a political firestorm when he told lawmakers during a hearing earlier this month that he believed "spying did occur" against's campaign during the 2016 election.

"I think spying did occur. The question is whether it was predicated, adequately predicated,” Barr said.

Pressed later on his comments, he added that he was "not saying improper surveillance occurred. I am saying I am concerned about it, and I am looking into it."

In addition to a briefing, Grassley and Johnson are asking Barr to detail the "nature and extent" of his review, how he plans to get information from individuals who have left the FBI, what steps he has taken to investigate if the FBI had "unauthorized contacts" with reporters and if he would share his findings with Congress once finished.

Grassley and Johnson also want to know how many counter-intelligence briefings were provided to Trump administration officials during the transition period leading up to the inauguration.