Senate Judiciary Committee Chairman Lindsey Graham told Fox News' Sean Hannity on Tuesday that Special Counsel Robert Mueller's investigation is "case closed" but the origins of the probe need to be looked at as thoroughly as the FBI's investigation of President Trump.

"Somebody needs to look at this like they looked at Trump," Graham said during an appearance on "Hannity" on Tuesday.

"We have got to get to the bottom of it and make sure it never happens again," the South Carolina Republican added.

TRUMP CAMPAIGN GOES ON POST-MUELLER ATTACK AGAINST 'OBAMA-ERA DOJ AND FBI,' WARNS 'JUSTICE WILL BE SERVED'

Mueller found no evidence that Trump or his campaign coordinated with the Russians to interfere in the election. But Mueller did not come to a conclusion on whether the president obstructed justice.

In the interview, Graham said the FISA warrant to wiretap former Trump campaign aide Carter Page was issued on the basis of the claims made in ex-British spy Christopher Steele's unverified dossier and would not have been granted otherwise. Graham and Hannity questioned why Mueller didn't investigate further into the origins of the Steele dossier, and when exactly he became aware that there wasn't evidence of collusion.

KELLYANNE CONWAY, AFTER MUELLER REPORT'S RELEASE, SAYS PRESS APOLOGIES ARE IN ORDER

"What I want to know is: when did [Mueller] know there was no conspiracy with The Trump campaign and Russia as it relates to collusion of any kind?" Hannity asked. "Why was he not concerned about Hillary's dirty Russian dossier when he had plenty of time to look into medallions and laws and taxes?

"I would think the Russian dossier would have been important to Robert Mueller," Hannity added.