National Security documents related to simulated attacks at the Super Bowl were left inside the seat-back pocket of an airplane and discovered by a CNN employee.

The sensitive materials, marked "For Official Use Only" and "important for national security," consisted of reports analyzing the response to a simulated Anthrax attack, reports the New York Daily News.

In December 2017, a CNN employee discovered the documents on a commercial plane, along with other sensitive Department of Homeland Security materials.

Those who possessed the documents were instructed to keep them locked up, never share the contents with anyone not on a "need-to-know" basis, and shred them prior to discarding them.

The employee also found travel documents for a government scientist in charge of BioWatch, a DHS program that conducted the simulated attacks in preparation for the big game in Minneapolis on Feb. 4, according to CNN.

According to the reports obtained by CNN, there were several areas that needed improvement and that "some local law enforcement and emergency management agencies possess only a cursory knowledge of the BioWatch program and its mission."

A DHS official told CNN the documents were the subject of an "operational review."