Rep. Devin Nunes, R-Calif., said on Monday the FBI has "something to hide" about Maltese academic Joseph Mifsud, the man who told former Trump campaign adviser George Papadopoulos the Russians had damaging information about Hillary Clinton.

During a Fox News interview, the House Intelligence Committee ranking member said he has sent two letters this month to the Central Intelligence Agency, FBI, National Security Agency, and State Department asking for all documents they have on Mifsud.

Nunes said all but the FBI are cooperating.

"The FBI is not cooperating, per usual, which means they've got something to hide," he said.

Mifsud, a London-based professor and former Maltese diplomat, has long been suspected of deep ties to Russian intelligence.

Although special counsel Robert Mueller's team portrayed Mifsud as a Russian asset with close ties to Russian President Vladimir Putin in their 448-page report, Nunes has said they decided to "cherry pick" information from news reports, leaving out that he described as a Western intelligence asset. Nunes specifically noted that Mifsud has a lot of ties to U.S., British, and Italian intelligence services.

"It is impossible that Mifsud is a Russian asset," Nunes said Monday. "He is a former diplomat with the Malta government. He lived in Italy. He worked and taught FBI, trained FBI officials, and worked with FBI officials."

Mueller's report, released last month with redactions, states that Mifsud traveled to Moscow in April 2016, after which he met Papadopoulos in London. It was at this meeting that Mifsud informed Papadopoulos that during his trip he learned that the Russians had “dirt” on Clinton, who served as secretary of state from 2009 to 2013 and was President Trump's Democratic rival in the 2016 election.

Papadopoulos later repeated this claim to Australian diplomat Alexander Downer, who informed the U.S. government and prompted the original counterintelligence investigation into Trump's campaign in July 2016.

Although Papadopoulos, who pleaded guilty to lying to the FBI, told investigators Mifsud talked to him about the Russians having "thousands" of Clinton emails, Mifsud denied to the FBI he knew or mentioned anything about emails.