The House Oversight Committee’s first closed-door, transcribed meeting investigating former President Joe Biden’s mental acuity began Tuesday with former White House Domestic Policy Council Director Neera Tanden appearing for questioning on Capitol Hill.

Committee Chairman James Comer is investigating Biden’s health and mental “decline,” as well as the use of an autopen for pardons and other executive actions.

“This is the first of what will be many interviews with people we believe were involved in the autopen scandal in the Biden administration,” Comer told reporters Tuesday morning. “I think the American people want to know, I think there’s a huge level of curiosity in the press corps [with] respect to who was actually calling the shots in the Biden administration.”

Following the introductory portion of the meeting, Comer said Republicans wrapped a “good hour,” while Rep. Wesley Bell, D-Mo., called it an “extraordinary waste of time.”

Tanden was nominated by Biden to be the director of the Office of Management and Budget but ultimately withdrew her nomination after facing a bruising confirmation battle and bipartisan criticism over her past tweets that attacked members of Congress.

In addition to Tanden, additional former Biden senior aides are expected to sit down for interviews in the coming weeks without being subpoenaed, including Anthony Bernal, Ashley Williams and Annie Tomasini.

Dr. Kevin O’Connor, the former White House physician for Biden, will appear under subpoena before the committee for a closed, transcribed interview on July 9, a source familiar with the committee’s plans told ABC News.

ABC News’ Lauren Peller contributed to this report.