President Donald Trump's serving top aide, Stephen Miller, was questioned for hours on Thursday by the congressional committee investigating the January 6, 2021 insurrection.

During the Trump administration, Miller was a senior policy advisor and a key influence on many of the Republican's policies. He had already opposed the committee's attempts, filing a lawsuit last month to overturn a demand for his phone records.

According to a person familiar with the situation who spoke on the condition of anonymity to disclose private testimony, Miller was interviewed for about eight hours. A committee representative said the panel had no comment, and Miller did not immediately respond to a message requesting comment.

Miller's appearance is the latest in a string of meetings the committee has had with members of Trump's inner circle as legislators get closer to the former President by questioning those who were with him on the day of the attack or were his confidants in the weeks leading up to it.

Trump's family questioned 

His presence comes only weeks after Ivanka Trump and her husband, Jared Kushner, agreed to meet with congressional investigators after the committee first approached them.

Members of the panel agreed that Kushner's testimony, which lasted more than six hours in late March, was beneficial. Ivanka Trump, who was in the White House with her father on January 6, was questioned for eight hours last week as congressional investigators attempted to put together her father's failed effort to delay the certification of the 2020 election results.

In November, the panel nine-member subpoenaed the former Trump advisor, along with Steve Bannon and former press secretary Kayleigh McEnany. The panel's chairman, Rep. Bennie Thompson, D-Miss., stated at the time that Miller was aware of and had participated in "efforts to propagate false information about purported voter fraud" and had encouraged state legislators to change the outcome of the 2020 election by designating substitute electors.

Thompson has also stated that Miller assisted in the preparation of Trump's remarks for a rally on the Ellipse before the insurgency and was present when Trump spoke.

Read more: Trump's kids refuse testifying in father's corruption

Last month, the House decided to charge former Trump advisors Peter Navarro and Dan Scavino in contempt of Congress for their month-long refusal to comply with subpoenas.

The move was the third time the panel has referred people in the former president’s orbit to the Justice Department for potential prosecution for contempt. The first two referrals, sent late last year, were for former White House chief of staff Mark Meadows and Bannon.