(CNN) -- A "suspicious item" at the Nevada National Security Site caused officials to scramble Tuesday, but it turned out to be "a non-threatening item," a spokesman for the site told CNN.
Federal and local officials were involved in the incident, which began to unfold around 4 p.m. (7 p.m. ET), when a "suspicious item" was discovered outside the device assembly facility security perimeter fence, said Dave Taylor, the spokesman.
About three hours later, the non-threatening nature of the item was discovered.
"We acted out of an abundance of caution," said Dante Pistone, another site spokesman. "There will be a lot of followup on this."
At 1,375 square miles, the site is larger than Rhode Island. It has been the site of more than four decades of testing of nuclear weapons.
Congress created the NNSA in 2000 as a semi-autonomous agency within the U.S. Department of Energy responsible for enhancing national security through the military application of nuclear energy.
According to the site's website, "NNSA maintains and enhances the safety, security, reliability and performance of the U.S. nuclear weapons stockpile without nuclear testing; works to reduce global danger from weapons of mass destruction; provides the U.S. Navy with safe and effective nuclear propulsion; and responds to nuclear and radiological emergencies in the U.S. and abroad."
CNN's Dana Ford, Amanda Watts and Tom Watkins contributed to this report.