Several U.S. Secret Service agents connected to former President Trump have been subpoenaed and are expected to testify before a Washington, D.C., grand jury likely on Friday this week.

The grand jury appearances are related to Special Counsel Jack Smith's probe into the handling of classified documents at Trump's personal estate, Mar-a-Lago.

A source familiar with the probe did not give a definitive number of agents involved, but confirmed the April 7 scheduled testimony.

The development in this case comes as Trump is scheduled to appear in court Tuesday to be arraigned following his indictment last week related to hush money payments made to a porn star in 2016.

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Donald Trump

Former President Trump. (SAUL LOEB/AFP via Getty Images)

A spokesperson for Secret Service said the agency has no comment. A spokesperson for Smith also declined to comment.

Trump's legal team has been largely unsuccessful in fighting subpoenas and other actions from Smith's team. Earlier this month, a judge ruled one of Trump's lawyer, Evan Corcoran, must testify before the grand jury related to the probe.

Smith's team is alleging that Trump mislead his attorneys about the classified documents stored at his home.

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A secret service agent tells passerby to keep moving, as he stands guard on the wall surrounding former President Donald Trumps Mar-a-Lago estate

A Secret Service agent tells passerby to keep moving, as he stands guard on the wall surrounding former President Trump's Mar-a-Lago. (AP Photo/Rebecca Blackwell)

Trump has forcefully disputed that claim.

Attorney General Merrick Garland assigned Smith as special counsel on Nov. 18 to investigate the matter, which has unfolded since FBI agents raided Mar-a-Lago on Aug 8., and seized classified records, including some marked as top secret, according to a warrant and property receipt.

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U.S. Magistrate Judge Bruce Reinhart signed the warrant, giving agents the authority to seize "all physical documents and records constituting evidence, contraband, fruits of crime, or other items illegally possessed" in violation of U.S. Code, including documents with classification markings and presidential records created between Jan. 20, 2017, and Jan. 20, 2021.

Donald Trump

Former President Trump speaks during a rally at the Waco Regional Airport. (Photo by Brandon Bell/Getty Images)

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The property receipt showed FBI agents took approximately 20 boxes of items from the premises, including one set of documents marked as "Various classified/TS/SCI documents," which refers to top secret/sensitive compartmented information.