(CNN) The Justice Department is opposing the release of details in an affidavit that lays out the argument that investigators made to a federal magistrate judge explaining the probable cause it had to search former President Donald Trump's Mar-a-Lago estate last week. In their new filing arguing for some continued secrecy, the Justice Department made clear the seriousness of the ongoing criminal investigation, saying it "implicates highly classified materials." "The fact that this investigation implicates highly classified materials further underscores the need to protect the integrity of the investigation and exacerbates the potential harm if information is disclosed to the public prematurely or improperly." Media organizations including CNN had asked for the affidavit to be unsealed after the search last week at Trump's Palm Beach, Florida, club and residence. The Justice Department said in its filing that disclosing the affidavit details "at this juncture" would "cause significant and irreparable damage to this ongoing criminal investigation."