In a shocking revelation that recalls the Anthrax scares of the early 2000s, CNN reported Tuesday that two pieces of mail delivered to a Pentagon mail facility tested positive for ricin, a deadly poison that was prominently featured in the television show "Breaking Bad."

And what's even more alarming, the envelopes were addressed to Secretary of Defense James Mattis and to Chief of Naval Operations Admiral John Richardson, the FBI said.

CNN reporting a piece of mail delivered to a Pentagon mail facility tested positive for ricin. That's not good. — Josh Rogin (@joshrogin) October 2, 2018

Here's more from CNN:

Two pieces of mail delivered to the Pentagon mail facility on Monday have initially tested positive for ricin, according to a US defense official. The mail facility is in a separate building on the grounds of the Pentagon and the piece of mail which tested positive never entered the Pentagon building. All mail delivered to the Pentagon Monday was put into quarantine, according to the official. The FBI and the Pentagon Force Protection Agency are responding and further testing is expected to be done by the FBI, the officials said. Ricin is a highly toxic compound that is extracted from castor beans and has been used in terror plots. It can be used in powder, pellet, mist or acid form. If ingested, it causes nausea, vomiting and internal bleeding of the stomach and intestines, followed by failure of the liver, spleen and kidneys, and death by collapse of the circulatory system.

This is a developing story. Check back for updates...