Washington (CNN) House Intelligence Chairman Devin Nunes said Monday most names were masked in documents he said showed President Donald Trump and his associates may have had their communications incidentally collected by US intelligence.

Nunes was describing his findings as he defended himself on CNN's "The Situation Room with Wolf Blitzer" from a wave of criticism following the revelation he visited White House grounds last week to access the information.

"It was pretty clear who they were talking about," Nunes said, adding, "For the most part, they were masked."

He said other names were unmasked and he wanted to get to the bottom of why they were.

Nunes said he had to view the classified documents, which he stressed were unrelated to Russia, in an Executive Branch location because they intelligence community had not yet provided them to Congress.

"The Congress has not been given this information, these documents, and that's the problem," Nunes said. "There was no way I could view that because they couldn't get it to the House Intelligence Committee."

Nunes has come under fire for his perceived conflict of interest leading an investigation that deals in part with the Trump campaign's potential ties to Russia, which the US intelligence community accused of attempting to influence the presidential election.

His Democratic counterpart on the committee, Rep. Adam Schiff, called for his recusal from the investigation Monday evening.

Nunes forcefully defended himself and said multiple times that the documents he viewed on White House grounds last week and briefed Trump personally on had nothing to do with Russia.

He said the documents he reviewed came from after the election, during which time Trump and his team were communicating with foreign officials as they transitioned into government.

"I was very concerned, and I thought that the President of the United States should know, and that's why I went and told him," Nunes said.

When the United States spies on the conversations of people overseas, the law requires it obfuscate the identities of anyone from the US who happens to be involved in the conversation.

Some within the intelligence and law enforcement communities may "unmask" the US person, but Nunes said he was worried about how and why Trump and members of his transition team could have been unmasked following legal surveillance collection.

Nunes said his committee had requested "appropriate intelligence agencies" provide it with the names of every US person unmasked going back for months. He anticipated the National Security Agency providing the information this week.

Nunes, a longtime overseer of the intelligence community, expressed concern in his interview that Trump and members of his transition team could have their privacy violated via incidental collection in the course of US surveillance.

"As somebody who supports our national security apparatus, it bothered me that this level of information would be included in intelligence reports because it just wasn't necessary," Nunes said.

Ex-national security adviser Michael Flynn exited his role in the Trump White House after media reports citing government officials emerged saying his communications with Russian ambassador Sergey Kislyak had been captured by US intelligence as part of its surveillance of Kislyak.