Update 10:13 a.m. EDT Oct. 3: Fox News reported that the return address of one of the envelope mailed to the Pentagon has lead officials to a former U.S. Navy sailor. Officials believe the items sent to Not only the White House, but also the Pentagon and a suspicious letter delivered to Sen. Ted Cruz's office in Texas were part of a coordinated effort, Fox News's Lucas Tomlinson reported.
Original report: Two pieces of mail addressed to the Pentagon have initially tested positive for the deadly chemical ricin, according to reports.
Two defense officials told CNN that the mail was delivered to the Pentagon's mail facility, but it did not enter the Pentagon itself. The mail facility is a separate building.
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CNN's Barbara Starr is reporting that additional testing of two envelopes is underway. The mail that was delivered Monday to the facility is under quarantine.
The FBI is leading the investigation, the Examiner reported.
There are no reports of anyone falling ill because of the suspected substance, the Examiner reported.
The pieces of mail were intended for Secretary of Defense James Mattis and Chief of Naval Operations Admiral John Richardson, CNN reported.
A third envelope was deemed suspicious and was addressed to President Donald Trump, Fox News reported. The envelope in question did not enter the White House, according to Fox News.
A Pentagon spokesman has confirmed that a suspicious substance was found during a screening process.
"On Monday, the Pentagon Force Protection Agency detected a suspicious substance during mail screening at the Pentagon's remote screening facility," Col. Rob Manning told Fox News in a statement. "The envelopes were taken by the FBI this morning for further analysis. All USPS mail received at the Pentagon mail screening facility yesterday is currently under quarantine and poses no threat to Pentagon personnel."
CNN reported that the FBI also made the following statement:
"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."
After the Sept. 11 attacks, the Pentagon built an underground mail processing facility that screens all deliveries.
According to the official history of the Pentagon, it is the center of the country's military power. It holds the Department of Defense, office of the Secretary of Defense, the Joint Chiefs of Staff and headquarters for the branches of the military.
It was built from 1941 to 1943.
It has more than 6 million square feet and is one of the world's largest office buildings, according to History.com.
More than 20,000 people work in the Pentagon, according to CNN.
Ricin is one of the easiest poisons to make and can take several forms, according to Fox News. It is found in castor beans and the waste from the process of making castor oil is where ricin comes from, according to the Centers for Disease Control and Prevention.
Check back for the latest on this developing story.