A bomb threat to multiple, unspecified buildings at Princeton University Tuesday morning resulted in the evacuation of a large part of the campus and an investigation involving local, state, and federal law enforcement agencies assisting the University’s Department of Public Safety. At press time, no explosives had been found.

Helicopters swirled overhead as police worked to get some 6,500 people off the campus during the late morning hours. Those who drove to work were instructed to go home rather than stick around waiting for updates. Those without cars, including students attending early summer programs, were evacuated to the Princeton Public Library, the Arts Council of Princeton, and The Nassau Inn, all of which agreed to offer their assistance.

“This is NOT a test,” the e-mail alert warned. “There has been a bomb threat to multiple unspecified campus buildings. Please evacuate the campus and all University offices immediately and go home unless otherwise directed by your supervisor. Public Safety officers and Princeton Police will direct drivers to leave the campus and those without cars will be directed to evacuation sites. You will receive an update later today. Do not return to campus for any reason until advised otherwise.”

The University received a bomb threat in the morning from an unidentified caller saying bombs had been placed in various campus buildings. The caller warned that the school had two hours to get everyone out. By 9:30 a.m., the Princeton Police Department had been notified by the University’s Department of Public Safety. University spokesman Martin Mbugua could not say specifically which buildings were affected by the threat. “It’s part of the ongoing investigation and I cannot go into detail at this time,” he said yesterday afternoon while waiting for the FBI and bomb-sniffing dogs to check the campus.

According to Sergeant Michael R. Cifelli of the Princeton Police Department, the local police were among several law enforcement agencies including the New Jersey State Police, the FBI, and NJ Transit officers, to assist with the evacuation and investigation. The evacuation snarled traffic on some area streets. Roads from Route 1 into Princeton were closed off, and people were advised to avoid downtown. Service on the Dinky train was suspended for a short period of time.

While there were no threats to other parts of Princeton, precautions were taken. Superintendent of Schools Judy Wilson sent a message to parents saying police had advised them “to move about our days in the schools as usual. However, I have ordered there be no outside student activity. Several roads near the University are blocked off so buses and cars will be rerouted until the campus is cleared for re-occupancy.”

By late afternoon, news trucks from New York and Philadelphia television stations were lined up along Nassau Street opposite the University campus, and on Washington Road in front of the Woodrow Wilson School. Guards were stationed at most entrances to the campus to keep people out. Where guards were not on duty, yellow police tape was in place. Tiger Transit was suspended until Wednesday morning.

By 3:30 p.m., the University reported on its website that “significant progress” had been made. “The searches are expected to continue for a few hours more, and University officials hope to reopen campus this evening,” it read. “However, no decision to reopen will be made until the searches are completed.”

The threats to the University were among several around the United States on Monday and Tuesday. One triggered a three-hour evacuation of Virginia’s Richmond International Airport on Tuesday morning. Another forced the evacuation of three state office buildings near Georgia’s Capitol building in Atlanta. On Monday, a Texas-bound Southwest Airlines jetliner was diverted to Phoenix after taking off from Los Angeles following a telephoned bomb threat.