Two people were rushed to hospital Tuesday following a white powder scare at Sen. Ted Cruz's campaign headquarters in Houston, Texas.

The office was evacuated and a hazmat crew from the Houston Fire Department dispatched after a package addressed to Cruz's team containing "a white powdery substance" was opened in the building's lobby.

Houston Fire Department later tweeted that the evacuation order had been lifted and "all tests were negative" for any hazardous material.

Cruz spokeswoman Catherine Frazier told the Associated Press no campaign staffers were hospitalized due to the incident.

The scare comes on the same day two suspicious envelopes mailed to the Pentagon on Monday tested positive for ricin. The discovery prompted a shutdown of a mail processing facility that is separate from the Pentagon itself. No one is reported to be suffering any ill effects from exposure to the substance.

Ricin is a deadly toxin that is naturally occurring in castor beans.