Police swept the Maricopa High campus after threats were faxed to the school warning of a bomb and a planned kidnapping.
The "all-clear" was given at around 10:40 a.m. after authorities said nothing was found.
The same school threat was faxed to schools in Atlanta, GA, and McDermott, OH, police said.
Maricopa High canceled classes after staff received the threats early Tuesday morning.
"There were threats of possibly trying to kidnap administrators,"Maricopa Police spokesman Ricardo Alvarado said. "There were threats of a bomb."
The school called police and officers set up a perimeter.
At the time of threat, no students were present, Alvarado said. Staff and faculty, however, were inside.
Police, along with the US Marshals Office and troopers from the Arizona Department of Public Safety, were at the school conducting the search.
The Chandler Police Department also deployed its bomb-sniffing dog.
"They're looking suspicious packages or anything out of place," Alvarado said.
The students who were all accounted for and students that ride the bus were held in a safe location off campus.
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