The House Oversight Committee has learned that President Joe Biden's autopen was routinely used —even while he was physically present in the White House, Chairman James Comer told Newsmax Thursday.

The committee is making "a lot of progress" in its investigation into the use of an autopen to sign documents during the Biden administration, especially during times when Biden was reportedly in the White House, the Kentucky Republican told "Greg Kelly Reports."

"We've got a big list of people to bring in. We're just going to follow the trail to see who is actually calling the shots and operating the autopen in the Biden White House," he said.

Comer said the committee interviewed Neera Tanden earlier in the week. Tanden served as Biden's staff secretary, managing documents that reached the president's desk and controlling the use of the autopen — a mechanical device that replicates a signature.

According to Comer, Tanden was "a good witness" and "very forthcoming" in her answers.

"She admitted that she was in charge of the documents into and out of the Oval Office, Joe Biden's desk. And she had authority to use the autopen," Comer said.

"She operated the autopen, but she was taking directions from what appears to be Ron Klain and others on the inside," Comer said, referencing Biden's former chief of staff. "She wasn't the one determined what to sign with the autopen and what not to sign.

"Neera Tanden didn't see Joe Biden ever authorize by signing his initials on the memos that she would receive that would say to use the autopen. Joe Biden wasn't around her when the autopen was in use, he said.

"We know that many times the autopen was used when Joe Biden was in the White House. Why didn't you just have Joe Biden sign it right there?"

The committee, Comer said, will next focus on "the people on the inside" who Tanden said were directing her actions. Subpoenas have already been issued, including for Dr. Kevin O'Connor, Biden's personal physician.

"We've subpoenaed several people, including Dr. O'Connor. We have a lot of questions about the medical reports that Dr. O'Connor published," he said.

"He published report after report saying Joe Biden was in tip-top physical condition. Now we know he has, you know, stage three cancer.

"We know that from the debate performance and from [Jake] Tapper's book and other interviews that Joe Biden was in decline."

Comer said the committee is pursuing evidence that Biden "wasn't calling the shots," citing accounts from journalists and books that suggest Biden may have been in cognitive decline.

"If someone was using Joe Biden's signature — essentially forging his signature — then those pardons and those executive orders could be declared null and void," Comer said.

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