Two parcels sent to Pentagon test positive for ricin. Here's what the FBI is saying.

Two envelopes sent to the Pentagon have initially tested positive for ricin, according to a Defense Department spokesperson, CNN reported.

What are the details?

Officials discovered the packages during screening on Monday and turned over the parcels to the FBI for further analysis.

The packages were addressed to Defense Secretary Jim Mattis and Adm. John Richardson, who is chief of naval operations. Specific information about the packages has yet to be released.

As a result of the questionable packages, the Pentagon's mail is currently under quarantine.

Col. Rob Manning, a Pentagon spokesperson, said that the mail facility is on Pentagon grounds, but is not housed in the main building, where the offices of the defense secretary are located.

"On Monday, the Pentagon Force Protection Agency detected a suspicious substance during mail screening at the Pentagon's remote screening facility," Manning said in an official statement. "The envelopes were taken by the FBI this morning for further analysis."

The FBI also issued a statement, confirming that they had taken possession of the parcels that tested positive for the deadly substance: "On Tuesday, October 2, 2018, in coordination with the Pentagon Force Protection Agency, FBI Special Agents took possession of two suspicious envelopes that had been screened at the Pentagon mail facility. Those envelopes are currently undergoing further testing. As this is ongoing, we will have no further comment."

What is ricin, anyway?

Ricin is a naturally occurring toxic compound and can be made from castor beans, which can then be turned into powder, according to CNN.

Ricin, if ingested, can cause nausea, vomiting, and internal bleeding of the digestive system. The hepatic system can also fail, and the person affected by the toxic compound can die from circulatory system collapse.

Ricin has often been used in terror plots.