CNN —

       At least two dozen people – from Mar-a-Lago resort staff to members of Donald Trump’s inner circle at the Florida estate – have been subpoenaed to testify to a federal grand jury that’s investigating the former president’s handling of classified documents, multiple sources familiar with the investigation told CNN.

       On Thursday, Trump’s communications aide Margo Martin, who worked in the White House and then moved with Trump to Florida, appeared before the grand jury in Washington, DC. One of special counsel Jack Smith’s senior-most prosecutors was involved in the interview.

       Margo Martin, White House press assistant, listens during a news conference in the James S. Brady Press Briefing Room at the White House in Washington, DC on Wednesday, July 8, 2020.

       Al Drago/Bloomberg/Getty Images

       Martin, who is among a small group of former White House advisers who have remained employed by Trump after he left office, declined to answer any questions when approached by a CNN reporter.

       Smith has sought testimony from a range of people close to Trump – from his own attorneys who represent him in the matter to staffers who work on the grounds of Mar-a-Lago, including a housekeeper and restaurant servers, sources said.

       The staffers are of interest to investigators because of what they may have seen or heard while on their daily duties around the estate, including whether they saw boxes or documents in Trump’s office suite or elsewhere.

       “They’re casting an extremely wide net – anyone and everyone who might have seen something,” said one source familiar with the Justice Department’s efforts.

       For instance, federal investigators have talked to a Mar-a-Lago staff member seen on security camera footage moving boxes from a storage room with Trump aide Walt Nauta, who has already spoken with investigators.

       Many of the Mar-a-Lago staffers are being represented by counsel paid for by Trump entities, according to sources and federal elections records.

       The Justice Department has been investigating potential mishandling of national security records and possible obstruction for about a year. FBI agents recovered more than 100 classified documents during a search of Mar-a-Lago last summer. Since then, Trump’s legal team has turned over additional classified material.

       Judge James Boasberg in his chambers at the U.S. District Court for the District of Columbia in Washington, March 13, 2023. Boasberg will take over from Beryl A. Howell as the chief judge of the Federal District Court in Washington, a post that plays a key role in the special counsel investigations into Donald Trump. (Erin Schaff/The New York Times)

       Erin Schaff/The New York Times/Redux

       There's a new chief judge in DC who could help determine the fate of Donald Trump

       The federal probe previously subpoenaed top Trump advisers, such as former White House deputy chief of staff Dan Scavino and former Trump adviser and Pentagon official Kash Patel.

       Meanwhile, Smith continues to pursue Trump defense lawyer Evan Corcoran. In an earlier appearance before the grand jury, Corcoran declined to answer questions about his conversations with Trump related to the classified documents, citing attorney-client privilege. Prosecutors are asking a judge to find that he must answer because the conversations may have been part of advancing a crime or fraud.

       A ruling is expected from the DC District Court on Corcoran as early as this week.