Docs received from Mar-a-Lago in January were marked with most sensitive classification, Archives...

Documents found in 15 boxes that former President Donald Trump turned over from his Mar-a-Lago property in January were marked classified at a level suggesting they contained some of the government’s most sensitive secrets.

The National Archives and Records Administration (NARA) informed Trump's lawyers about the discovery in a May letter, which was posted on its website on Tuesday. The letter was first published on the website of conservative journalist John Solomon.

After Trump's lawyers turned over 15 boxes in January, officials at the archives identified items inside the boxes "marked as classified national security information, up to the level of top secret and including sensitive compartmented information and special access program materials," the letter said. That suggests Trump took home the most highly protected material in the U.S. government — material that, if disclosed, could betray sources and methods.