Top White House officials on Monday stood by President Trump’s charge that President Obama tapped his phones during last year’s campaign without providing additional evidence, as lawmakers and former intelligence officials sparred over the allegations.

Counselor Kellyanne Conway, asked directly on “Fox & Friends” when the president may have first heard of possible wiretapping in Trump Tower, said she would not “reveal that.”

But she noted “it’s a big place,” adding: “If we don’t know, then let’s find out together.”

At the same time, Conway said, “He’s the president of the United States. He has information and intelligence that the rest of us do not.”

Spokesman Sarah Huckabee Sanders said on NBC’s “Today” show that Trump firmly believes the allegations he made on Twitter over the weekend.

The explanations from Conway and other White House officials leave unclear what specific information Trump may have to bolster his Saturday morning claims about wiretapping under Obama.

Conway on Monday cited “credible news sources.”

When he blasted out the explosive allegations on Twitter, Trump may have been referring to a recently published Breitbart article that addressed claims from a Mark Levin radio segment about alleged efforts by the Obama administration to undermine the Trump campaign. The timeline was drawn from a range of other news reports and sources, including The New York Times, The Washington Post and The Guardian.

Obama's director of national intelligence, James Clapper, said nothing matching Trump's claims had taken place.

"Absolutely, I can deny it," Clapper, who left government when Trump took office, told NBC’s “Meet the Press.” Other Obama representatives also denied Trump's allegation.

But Conway on Monday pointed to comments made by Bush Attorney General Michael Mukasey on ABC’s “This Week.” He said he thinks Trump is right about surveillance, but that it was conducted under direction from the attorney general at the Justice Department.

Republican lawmakers generally have given a measured response to Trump’s claims, voicing a willingness to investigate the claims as the White House has requested, without affirming them.

Senate Intelligence Committee Chairman Richard Burr, R-N.C., said in a statement that the panel "will follow the evidence where it leads, and we will continue to be guided by the intelligence and facts as we compile our findings."

Rep. Devin Nunes, R-Calif., chairman of the House Intelligence Committee, said in a statement that the committee "will make inquiries into whether the government was conducting surveillance activities on any political party's campaign officials or surrogates."

Rep. Trey Gowdy, R-S.C., told Fox News’ “America’s Newsroom” that he will need access to witnesses and documents.

“It’s really hard to cross-examine tweets,” he said, noting there would be a “paper trail.”

Trump's request carries some risk, particularly if the committees unearth damaging information about him or his associates. Committee Democrats will have access to the information and could wield anything negative against the president. Asking Congress to conduct a much broader investigation than originally envisioned also ensures the Russia issue will hang over the White House for months.

Josh Earnest, who was Obama's White House press secretary, said presidents do not have authority to unilaterally order the wiretapping of American citizens, as Trump has alleged was done to him. FBI investigators and Justice Department officials must seek approval from a federal judge for such a step. Earnest accused Trump of leveling the allegation to distract from the attention being given to the Russia issue.

Trump said in the tweets that he had "just found out" about being wiretapped. Unclear was whether he was referring to having learned through a briefing, a conversation or a media report.

The Associated Press contributed to this report.