Former FBI Director Jim Comey testified Thursday that out of "tens of thousands of investigations" the agency is conducting at the same time, President Donald Trump only ever asked him about one probe: the one into his ousted national security advisor Michael Flynn.

"No," Comey said when asked if Trump had ever questioned him about any other case.

"No," Comey said again when Sen. Mark Warner, D-Va., asked if Trump had ever asked about interfering in any other cases beside the one involving Flynn, and Flynn's contacts with Russians before and after the presidential election.

Comey, whom Trump fired in May, also told Warner during the hearing on Capitol Hill that he found it strange that Trump had asked at a meeting early this year whether he wanted to remain as FBI director.

"What was odd about it was he had already asked twice about it," Comey said, noting he already told the president he wanted to remain in his post.

Comey said he believed Trump was asking him that because "either he had concluded, or somebody told him, 'You already asked Comey to stay, and you didn't get anything for it.'"

"My common sense here is he's looking to get something in exchange in response to my request that I stay on my job," Comey said.

Comey said that during a Jan. 22 ceremony in the Blue Room at the White House, when Trump called him out of a crowd to shake his hand, "What the president whispered in my ear was, 'I really look forward to working with you.'"

Comey said he was "uneasy" about Trump's comments, which to him suggested a linkage between remaining on the job and keeping Trump happy.

He noted that Congress created a 10-year term for FBI directors specifically to insulate them from concerns that they would lose their job if they displeased a president.

And Comey referenced the symbol of justice, which is a woman standing blindfolded and holding a scale.

"You're not supposed to be peeking outside to see if your patron is pleased at what you're doing," he said.

Comey said that during a Feb. 14 meeting in the Oval Office at the White House, "my impression was something big is about to happen, I need to remember every word that is spoken," after Trump asked Comey's boss, Attorney General Jeff Sessions, and Trump's son-in-law, Jared Kushner, to leave so he could speak alone to the FBI director.

"My sense is the attorney general knew he should not have been leaving ... which is why he lingered," Comey said. He noted that Kushner also lingered.

But the two men left. And Trump then asked Comey to end the probe into Flynn, according to Comey, who memorialized the meeting right afterward in a memo.

In his prepared testimony, Comey wrote: "The President then returned to the topic of Mike Flynn, saying, 'He is a good guy and has been through a lot.' He repeated that Flynn hadn't done anything wrong on his calls with the Russians, but had misled the Vice President."

"He then said, 'I hope you can see your way clear to letting this go, to letting Flynn go. He is a good guy. I hope you can let this go.' I replied only that "he is a good guy." (In fact, I had a positive experience dealing with Mike Flynn when he was a colleague as Director of the Defense Intelligence Agency at the beginning of my term at FBI.) I did not say I would 'let this go,'" Comey said in his prepared remarks.

On Thursday, Comey told Warner, "I remember thinking this is a very disturbing development really important to our work. I need to document it."