Princeton University ordered the campus evacuated Tuesday due to a bomb threat to "multiple unspecified campus buildings."
A posting on the university website at 10:26 a.m. ET directed all students and employees to go home and "do not return to campus for any reason until advised otherwise."
The university said it is investigating the incident with "local, state and federal law enforcement agencies."
All employees except for essential public safety and facilities staff were directed not to return to work until tomorrow.
Regular classes have ended for the summer and commencement was last Tuesday, according to a tweet from the university. Most students left campus days or weeks ago.
The Ivy League school, located in central New Jersey about 50 miles southwest of New York City, is home to approximately 5,000 undergraduate students, 2,500 graduate students and 1,100 faculty. Its campus comprises 180 buildings on 500 acres. The Princeton area has about 30,000 residents.
About 98% of undergraduate students live on campus, according to the university website. It was not immediately known whether campus residence halls were being evacuated.
The Princeton threat was one of several incidents on Tuesday:
--A bomb threat near the Georgia state Capitol in Atlanta forced the evacuation of five buildings housing the state attorney general's office, the state Supreme Court., and the Georgia Court of Appeals. Two of the buildings were cleared by noon and employees were allowed to return. Three buildings were still being checked.
--A threatening phone call shortly after 6 a.m. prompted an evacuation at Virginia's Richmond International Airport. Flights were halted and canine units were brought in to sweep the terminals and the parking decks. Nothing was found, and by 9:45 a.m. ET the airport had reopened.
Contributing: The Associated Press
John Riley, USA TODAY