(Reuters) - At least two people were taken to a hospital after a white powdery substance was found in a Houston building where U.S. Senator Ted Cruz’s campaign office is located, but tests showed the substance to be non-hazardous, fire officials said on Tuesday.

The substance was found in the Phoenix Tower building in Houston, the city’s fire department said on Twitter.

“It was a false alarm, all’s fine,” said Roxann Malloy, a Cruz campaign volunteer who answered the phone at the Republican senator’s campaign office. Cruz is seeking re-election in the Nov. 6 elections.

She said the powder was found in a package a few floors below the campaign office.

Cruz said it was unclear what had happened.

“It may be that this was a hoax or someone trying to cause terror,” Cruz told reporters in the hallway of a Senate office building in Washington. “We don’t know and I’m sure it will be investigated further.”

The floor was briefly evacuated and people who had contact with the substance were taken to the hospital as a precaution, the fire department said.

The Houston Police Department said on Twitter it was assisting the FBI with the investigation.