Pentagon: Substance in Suspicious Letters Castor Seeds, Not Ricin

The substance found in envelopes sent to the Pentagon and White House reportedly contained castor seeds and not the deadly poison ricin.

"According to our preliminary analysis, the substance was castor seeds, from which ricin is derived. The FBI is still investigating," chief Pentagon spokesperson Dana White said, ABC News reported.

According to ABC News, which cited an unnamed source, one of the four envelopes had a return address, which the FBI is now pursuing as a lead.

On Tuesday, two envelopes suspected of containing ricin poison were identified in the Pentagon's Central Processing Center, according to a U.S. official.

The Secret Service reported one of the envelopes was addressed to Defense Secretary James Mattis. The other suspicious envelope was addressed to President Donald Trump, though that envelope was not received nor did it enter the White House.

USA Today reported a white, powdery substance sent Tuesday to the Houston campaign headquarters of Sen. Ted Cruz turned out to be a false alarm.

The Houston Fire Department evacuated the floor in a Texas high-rise where Cruz's offices are located but later said tests on the powdery substance there were negative for the poison ricin.

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