Authorities rescinded the evacuation order Wednesday afternoon after tracing the leak of silicon tetrafluoride to a faulty valve on the tanker, said Robin Gurgainus, a spokesman for Johnston County.

The truck was contracted by Transwood Carriers of Nebraska, Gurgainus said. It was transporting 12,500 pounds of the gas from PCS Phosphates in Aurora to Texas.

Two people were in the truck when Greg Mabley, the driver, noticed the leak about 3 a.m. Wednesday, Gurgainus said. One person in the truck was not hurt; the other was treated at Johnston County Memorial Hospital.

Silicon tetrafluoride is colorless and nonflammable with a pungent odor similar to that of hydrochloric acid, according to a Web site maintained by the National Oceanic and Atmospheric Administration. The chemical can be fatal if inhaled, and the vapors are extremely irritating and corrosive, according to NOAA.