WASHINGTON (NewsNation) — The special counsel overseeing the criminal investigation of former President Donald Trump has subpoenaed Trump’s daughter Ivanka and her husband Jared Kushner, according to a new report.

The subpoenas by special council Jack Smith, which demand the couple’s testimony before a grand jury, are related to his probe of Trump’s efforts to remain in the White House after losing the 2020 election of President Joe Biden and the Jan. 6, 2021, U.S Capitol riots, according to The New York Times.

Smith has also summoned other members of Trump’s innermost circle in recent weeks, including former Vice President Mike Pence and former Trump chief of staff Mark Meadows.

The escalation of Smith’s investigation, including approaching prominent individuals connected to the matter, means the probe may be nearing its conclusion. Smith is also investigating Trump’s handling of classified information. 

Trump, who has had an adversarial relationship with Smith, has attempted to block witnesses from testifying in the investigation on the grounds of executive privilege. Pence has also said that he plans to fight Smith’s subpoena.

Smith’s subpoena of Ivanka Trump and Kushner also continues his push to crack the circle of the people who were closest to the former president on Jan. 6, 2021, as rioters stormed the U.S. Capitol. Ivanka Trump was with her father in the Oval Office that day, and Kushner was also at the White House. 

Both Ivanka Trump and Kushner also testified before the congressional committee that was investigating the event.

Both of them served as senior White House advisors to the former president.