Authorities are investigating a suspicious package that was found early Wednesday at a nuclear power plant west of Phoenix.

Maricopa County Sheriff's spokesman Brian Lee says security officers at the Palo Verde Nuclear Generating Station called them at about 5 a.m. after they found the suspicious package. A second call initially led to confusion that a second device may have been found, but that was quickly discounted.

Lee says a sheriff's bomb squad is investigating.

A spokesman for plant operator Arizona Public Service Co. says security guards found the suspicious package during a search of a vehicle at a checkpoint about a mile from the plant.

The plant is operating normally, but traffic in and out is stopped.