Security experts are sounding off about President Biden's handling of classified materials, suggesting that the documents could have been more susceptible to leaks than those found in former President Donald Trump's Mar-a-Lago estate last year.

Under scrutiny from Republicans, Attorney General Merrick Garland appointed a special counsel Thursday to investigate the classified materials, which Biden claims were "inadvertently misplaced."

The Justice Department escalated it to a special counsel investigation from a mere review after a second stash of classified documents was found inside the garage of Biden's Wilmington, Delaware, home. The first documents were found inside the Washington, D.C., offices of the Penn Biden Center think tank. Garland tapped Robert Hur, a former U.S. attorney, to handle the investigation.

Charles Marino, the CEO of Sentinel Security and a former Homeland Security Department advisor who specializes in law enforcement, told Fox News Digital that Biden's handling of the documents, compared to Trump's, could have resulted in greater potential for "leakage."

WHO HAD ACCESS TO BIDEN CLASSIFIED DOCUMENTS? REPUBLICAN DEMANDS WHITE HOUSE RELEASE DELAWARE VISITOR LOGS

Joe Biden

President Biden delivers remarks on the economy and inflation in the Eisenhower Executive Office Building on Jan. 12, 2023, in Washington, D.C. (Kevin Dietsch/Getty Images)

"The storage of classified documents was not authorized at any of these locations, however there are several distinctions with respect to the potential ‘leakage’ of the information contained within the documents via controls that would have likely prevented or limited unauthorized access to the locations," Marino said.

Noting that Trump "had the power to declassify whereas Joe Biden as vice president did not," Marino suggested that Trump's additional Secret Service protection granted the documents slightly more protection.

"Former Presidents continue to receive Secret Service protection and deploy security technologies, whereas former Vice Presidents do not, beyond an initial six-month extension. This means there was no US government provided security at the residence in Wilmington, Delaware, or at the Biden-UPenn think tank office in Washington, D.C. for close to six years," he said. 

"Former Presidents are eligible to continue to receive both secure communications and facilities. For example, former Presidents are eligible to request continuation of receiving the classified presidential daily briefings. Former Vice Presidents are not."

Biden's claim that he was unaware he possessed classified materials, according to Marino, also a former Secret Service special agent, adds to concern over how closely the documents at both locations were protected.

"Not knowing that one is in possession of classified documents, as Biden has claimed, means that there were absolutely no additional measures to safeguard and protect the information," he said. "Former President Trump acknowledged such possession, took steps to secure them in one location (although still not in accordance with storage requirements for classified info), and is still granted additional security resources for deterrence and detection."

Joe Biden and Donald Trump

Charles Marino, the CEO of Sentinel Security and a former Homeland Security Department advisor who specializes in law enforcement, told Fox that Biden's handling of the documents, as compared to Trump, could have resulted in greater potential for "leakage." (Pool/Getty Images | Erin Schaff/Getty Images)

DEMOCRATS SCRAMBLE TO DEFEND BIDEN'S HANDLING OF CLASSIFIED MATERIALS, POINT FINGERS AT TRUMP

Special counsel to the president Richard Sauber disclosed in a statement Saturday that five additional pages of documents with classified markings were found at Biden's Delaware home Thursday evening, making a total of six classified documents retrieved from the house — in addition to the documents discovered in the garage.

Sauber explained that when Biden's personal attorneys identified one classified document at Biden's home on Wednesday, they stopped searching for additional documents, because they lacked the security clearances necessary to view those materials.

The first batch of classified documents in Biden's possession was found at the Penn Biden Center on Nov. 2, just before the 2022 midterm elections, and not revealed until Monday. A search of Biden's garage at his Wilmington home was conducted on Dec. 20, and the remainder of the house, according to Biden's lawyers, was searched this week, when additional documents were discovered.

Bided answered a question Thursday from Fox News reporter Peter Doocy by claiming the classified documents were in a locked garage with his Corvette. "By the way, my Corvette’s in a locked garage, OK?" the president said. "So it's not like they’re sitting out in the street."

Highlighting the fact that it is "risky and irresponsible to keep classified information in an improperly secured location," Jamil Jaffer, founder and executive director of the National Security Institute, told Fox that Biden's handling of the documents is "certainly concerning."

"The fact that President Biden continued to find classified documents as recently as this past week, even after having first identified this problem in early November and having identified more documents in December, is certainly concerning," Jaffer said. "At the same time, it is also extremely concerning that classified documents were found in former President Trump’s possession long after he had been asked to turn any such documents over, and after he had received a subpoena for such documents."

Biden backs into Delaware driveway

Then-presidential candidate Joe Biden is seen backing into what appears to be his Wilmington, Delaware, driveway in a 2020 campaign video. (Joe Biden 2020)

"While it still remains unclear why President Biden had such documents in his possession long after he left office and in insecure locations, at least thus far he has not claimed, as former President Trump has, that the documents were appropriately removed, either because they were personal documents — which they are not — or that they had been properly declassified, which there is no evidence yet that they had been," he added.

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While there has been no confirmation of the information that was contained in the discovered documents, one was reportedly marked top secret, CNN reported this week based on a source familiar with the matter. The documents reportedly included intelligence memos and briefing documents on topics that included Ukraine, Iran and the United Kingdom, according to the source.

Biden's lawyers say they discovered no documents at Biden's residence in Rehoboth Beach, and Sauber reiterated Saturday that the White House would cooperate with Hur’s investigation.

Fox News Digital reached out to the White House for comment.

Fox News' Anders Hagstrom and Chris Pandolfo contributed to this article.