More than a dozen people who work at Mar-a-Lago, or who are in former President Donald Trump's inner circle at the resort, were served subpoenas to testify about Trump's handling of classified documents.
One source told CNN that investigators are "casting an extremely wide net — anyone and everyone who might have seen something" involving classified documents being kept at Mar-a-Lago is being subpoenaed.
Former White House aide Margo Martin, who joined Trump in Florida after he left office, testified before the grand jury this week but declined to answer questions from the press.
Former Pentagon special counsel Ryan Goodman told CNN's "OutFront" on Thursday that special counsel Jack Smith, who is investigating the classified documents, is looking to speak with people who are "invisible" to Trump
"They might be invisible to him. But they are the eyes and ears, and they can see things. Or they can know things might even be somewhat rumored, but then they can at least give the investigators leads, so they can tell the investigators who is present in different conversations," Goodman said.
He noted that investigators from the House select committee on the Capitol riot used a similar strategy last year.
"There are important lower-level White House staff that do give testimony for example, the person that greets Trump as he enters the White House after his Ellipse speech and tells him that there's rioting down at the Capitol, that's an important marker, but that was a lower-level staff person; he might not have noticed or thought about that conversation," Goodman said.