 -- The White House has invited the chairmen and ranking members of the House and Senate Intelligence committees to the White House to view documents discovered by National Security Council staff, press secretary Sean Spicer announced at Thursday's press briefing.

"What I’m suggesting is that there has been information that has ... come to light and we want to make sure that the people who are conducting the review have the information, have access to it," Spicer said.

When asked by ABC News' Cecilia Vega whether the materials validate President Donald Trump's claim that he and his associates were wiretapped under order from former President Barack Obama, Spicer said he didn't know.

"I have not seen the materials. It's members of the National Security [Council] who have come across these documents that want to make them available to the members leading the review," Spicer said.

The press secretary would neither confirm nor deny a report by The New York Times earlier in the day that two White House officials were the sources of the intelligence provided to House Intelligence Committee Chair Devin Nunes, R-California, on the White House grounds last week -- information about which Nunes later returned to brief Trump.

A week ago Spicer questioned why Nunes "would come up to brief the president on something that we gave him" and said the situation "doesn't really pass the smell test." At Thursday's briefing, Spicer said he "can’t get into" the chairman’s sources and again said he didn't know who let Nunes onto White House grounds March 21.

As he criticized the press for focusing on the "process" of the investigation rather than its "substance," Spicer maintained that the inquiry into Russia is being carried out in a "responsible way."

"I think this is being done in a responsible way where people are discussing what they know at an appropriate classification level and information is being shared," Spicer said.

Asked whether Trump had been briefed on the intelligence to be provided to the committee leaders, Spicer said he didn’t know.

Shortly after the White House briefing, Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee, expressed his "profound concern with how these materials are being made available to the committee."

"I have to say I'm more than perplexed for how these materials have been put forward and the motivations behind it and I think the White House has a lot of questions to answer," he said.

"Why all the cloak-and-dagger stuff? I think it's something we need to get to the bottom of," he added.

As for his own committee's work, which has been bogged down by partisan infighting, Schiff said he and Nunes have reached an agreement to invite FBI Director James Comey and NSA Director Mike Rogers to appear before the panel in a closed-door session.

He also didn't rule out asking the White House officials named in The New York Times story to appear before the committee.

"If it's necessary for us to interview these two individuals, then we should do so," he said.

ABC News' Meghan Keneally and Benjamin Siegel contributed to this report.