CBS News reports that documents marked "top secret" have been discovered among President Joe Biden's documents at the Penn Biden Center. 

Per the outlet: "The approximately 10 documents marked classified and discovered at the Penn Biden Center included top-secret material, according to a federal law enforcement official familiar with the investigation."

"Top secret is the highest of the three basic levels of classification: confidential, secret, and top secret," the outlet adds. "A leak of top secret information could cause "exceptionally grave damage."

This is the latest development in the Biden classified documents scandal.

Background

The classified documents were firt found at Biden's vice-presidential office in the Penn Biden Center for Diplomacy and Global Engagement in Washington.

The documents were discovered by Biden's personal attorneys just before the midterm elections, on Nov. 2. Richard Sauber, a special counsel to the president, claims that the documents were found when the attornies "were packing files housed in a locked closet to prepare to vacate office space at the Penn Biden Center in Washington, D.C."

Sauber says that the attornies promptly contacted the National Archive and handed over the documents.

Since then, more classified documents have been found in Biden's possession. This includes 10 classified documents at Biden's residence in Wilmington, Delaware.

So, it is now known that Biden has had at least 20 classified documents in his possession and 10 of them had a "top secret" marking.

The latest

Biden and the federal government have been facing a lot of criticism over this situation, particularly considering the apparent disparity in treatment between this situation and the classified documents situation involving former President Donald Trump - the one that culminated in an FBI raid on Trump's Mar-a-Lago estate.

Biden and his people have claimed that a significant difference between the two situations is that he has cooperated by turning the documents over to federal authorities, while Trump did not cooperate. Critics, however, disagree with this reading of the situation.

Attempting to suppress some of this criticism, U.S. Attorney General Merrick Garland has named a special counsel - Robert Hur - to oversee a U.S. Department of Justice (DOJ) investigation in the Biden classified documents scandal.

Still, it does not appear as though the federal agencies are pursuing this situation as vigorously as they pursued the Trump situation. And, critics remain skeptical about whether Biden is going to be held to the same standard.

Hur has vowed to investigate the matter with "fair, impartial, and dispassionate judgment," saying, "I intend to follow the facts swiftly and thoroughly, without fear or favor, and will honor the trust placed in me to perform this service."