BREAKING: Mike Pence testified for 7 hours TODAY before Federal grand jury inspecial counsel's probe into Trump’s involvement w/ January 6

Former Vice President Mike Pence appeared Thursday before the federal grand jury convened as part of the special counsel investigation into former President Donald Trump’s efforts to overturn his 2020 election loss and remain in power, according to a source familiar with the matter.

The testimony is a significant development in the special counsel’s probe, as Pence could provide critical insights into Trump’s thinking in the days leading up to the attack on the U.S. Capitol on Jan. 6. The former vice president published a memoir and Wall Street Journal opinion article detailing several of his interactions with Trump, but some details were left vague. Special counsel Jack Smith’s team is particularly interested in Trump’s efforts to try to block the certification of the election, NBC News previously reported.

Pence's appearance came amid an increased security presence at the federal courthouse in Washington on Thursday. NBC News spotted multiple black SUVs with tinted windows entering the parking garage in the morning. Two black SUVs entered the courthouse garage at around 9 a.m., an entrance that would allow witnesses to head up to the grand jury rooms on the third floor without being seen in the public areas of the courthouse.

The SUVs left the courthouse at about 4:30 p.m.

When reporters asked Chief Judge James Boasberg, who oversees grand jury proceedings, what was happening, he demurred.

A spokesman for special counsel Jack Smith declined to comment.

Last month, a federal judge ordered Pence to comply with a subpoena to testify and Trump failed in a bid to block his former vice president's testimony. On Wednesday, a federal appeals court rejected Trump's appeal.

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