The Pentagon and Ted Cruz's Houston office hit with potentially poisoned mail

The Pentagon has intercepted at least two packages thought to contain the poisonous substance known as ricin, The Associated Press reports.

The packages were caught Monday during a screening in a separate building on the Pentagon grounds, a spokesman tells AP. The spokesman wouldn't say who the packages were addressed to, but a U.S. official said they were headed for Defense Secretary Jim Mattis and Chief of Naval Operations John Richardson. All the mail from Monday is under quarantine and "poses no threat to Pentagon personnel," another spokesman said. Ricin is made from castor beans, and inhaling it could lead to low blood pressure and respiratory failure. The FBI is investigating the incident.

The Pentagon packages arrived Monday, but around noon on Tuesday, two people were hospitalized at Sen. Ted Cruz's (R-Texas) Houston campaign office after "apparently being exposed to a white powdery substance" in a piece of mail, the Houston Fire Department tweeted. Ricin can take such a form, but an investigation into the substance is still ongoing, Houston's ABC affiliate reports. The entire building was evacuated, though it has since reopened after hazardous substance testing proved negative.

The attacks are reminiscent of the ricin-filled letters sent to the White House and a Senate office in 2003 and 2004. No suspects in those attacks were ever apprehended.