Congressional investigators are demanding answers following revelations that Hillary Clinton and the Democratic National Committee help​ed​ fund a 2016 dossier containing information damaging to President Trump.

Sen. Susan Collins (R-Maine) on Sunday called for Clinton campaign manager John Podesta, former DNC Chair Debbie Wasserman Schultz and others to retestify before the Senate Intelligence Committee investigating Russian interference​ in the 2016 election.​

“They absolutely need to be recalled,” Collins, who serves on the Senate panel, told CBS’ “Face the Nation.” “It’s difficult to imagine that a campaign chairman, that the head of the DNC would not know of an expenditure of this magnitude and significance. But perhaps there’s something more going on here. But certainly it’s worth additional questioning of those two witnesses.”

The Washington Post reported that Clinton’s campaign and DNC lawyer Marc Elias retained​ ​the firm Fusion GPS to conduct opposition research​ on Trump.

Fusion GPS then hired Christopher Steele, a former British intelligence officer, who wrote the now-infamous dossier.

Campaign finance reports show both the Clinton campaign and DNC paid Elias’ law firm, Perkins Coie, millions of dollars. Neither disclosed how that money was funneled to Fusion GPS.

Rep. Trey Gowdy (R-SC), chair of the House Oversight Committee, suggested that paying a law firm for opposition research amounted to money laundering.

“I am interested . . . in sharing some memory tricks with folks at the DNC because no one can remember who paid $10 million to a law firm to do oppo research,” he told “Fox News Sunday.” “I find that stunning.”