The letters suspected of ricin did not contain a finite form of poison

Letters believed to contain deadly poison sent to the White House and Pentagon contained no finite form of ricin, a poison from castor seeds that can be deadly, law enforcement officials said on Wednesday .

Instead, they contained a primitive form or precursor that is not very dangerous, officials said.

When asked if any other similar letters had been found, a manager answered this question, but nothing is definitive yet.

Officials also said that they now believe that a separate letter found yesterday to Senator Ted Cruz, R-Tx., Campaign office in Houston is not related.

A flurry of suspicious envelopes addressed to prominent political figures have been received in the last two days.

On Tuesday, federal officials said that at least two envelopes, addressed to Secretary of Defense James Mattis, and the chief of naval operations, Admiral John Richardson, in a departmental mail processing center of the Defense, were suspected of containing the deadly toxin.

The FBI was conducting the investigation by testing these envelopes.

Later on Tuesday, the secret service announced in a statement that it intercepted a "suspicious envelope" addressed to the president.

The mail was intercepted outside the White House. The secret services did not provide any other details regarding the envelope.

And two people were hospitalized in Houston after the discovery of a "white powdery substance" in a letter addressed to the headquarters of Cruz's campaign, according to repressive sources. The package was opened in the lobby, which resulted in a temporary closure, according to Cruz's spokeswoman. No Cruz staffer was hospitalized during the incident, she said.