FBI spokeswoman Debbie Dujanovic Bertram tells The Associated Press that agents are searching the site for anything suspicious.
The Deseret News of Salt Lake City reported that authorities are using bomb-sniffing dogs.
The U.S. Army Corps of Engineers, which is in charge of the project, tells the AP it evacuated the construction site around 11:30 a.m. Monday.
The NSA broke ground on the $1.2 billion cyber security center in January.
Camp Williams is about 25 miles south of Salt Lake City.
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