Authorities are investigating a piece of mail with a white powdery substance that was sent to Sen. Ted Cruz Rafael (Ted) Edward CruzTrump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE's (R-Texas) campaign headquarters in Houston, a spokeswoman for Cruz's campaign said Tuesday.

Campaign staff reported the mail to authorities after opening it on Tuesday. A hazmat team and firefighters from the Houston Fire Department responded to the incident and were still at the scene early Tuesday afternoon.

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The campaign spokeswoman said Cruz's team can't say what the substance was.

The Houston Fire Department said on Twitter that two people were taken to the hospital Tuesday after being exposed to the substance. Neither of those people were members of Cruz's campaign staff, according to the spokeswoman.