First responders were called to the Houston campaign offices of Sen. Ted Cruz (R-TX) on Tuesday after staff received an envelope containing a white powdery substance.
Officials dispatched a HazMat team along with police and firefighters after a campaign staffer opened the letter, according to The Weekly Standard.
On Twitter, the Houston Fire Department noted that two people had been taken to the hospital after being exposed to the unknown substance.
A spokesperson for the Cruz campaign told The Hill that neither of the people that were transported to the hospital worked for the campaign.
The Houston Fire Department later lifted the evacuation order of the building and said that tests on the substance came back as negative.