Authorities are inspecting buildings at Princeton University after a bomb threat was reported this morning.

The Ivy League school says in a statement on its website that "there has been a bomb threat to multiple unspecified campus buildings."

Bomb-sniffing dogs were brought to the university. As of about 1:30 p.m., Princeton said the search was under way and expected to take several hours.

The campus was evacuated while university, local, state and federal authorities investigate the threat.

"Do not return to campus for any reason until advised otherwise," says the alert, which was issued shortly before 10:30 a.m.

In messages on Twitter and Facebook, the university is stressing to followers that the bomb-threat message is not a test.

There are no other threats in the town beyond the university, according to Princeton police.

Employees were informed that there was a "credible threat," workers told 6ABC. A university spokesman said the threat was reported by phone at about 9 a.m., according to the Newark Star-Ledger.

The spokesman told the Daily Princetonian that about 6,900 faculty, staff and students were evacuated today.

Several people at Princeton posted on Twitter that helicopters were hovering over the university.

Princeton's spring semester ended with commencement on June 4. The university doesn't have a regular summer term, its academic calendar says, though some summer courses are offered.

Most students left campus days or weeks ago, the university says.

Princeton says no employees other than essential workers from the public safety and facilities departments are expected to return to campus today.

Princeton police say recommended routes for those leaving the area are Route 206 north or southbound, and Route 27 northbound. The university says those leaving campus can go to Nassau Inn, Princeton Public Library or the Princeton Arts Council building.

Traffic into Princeton from Route 1 was closed for several hours, but has now re-opened.

New Jersey Transit said the Princeton shuttle service known as the "Dinky" was temporarily suspended in both directions. That service has been restored.

Princeton, tied with Harvard as the top-ranked university in the country by U.S. News and World Report, has about 180 buildings on 500 acres of land.

Contact Emily Babay at 215-854-2153 or Follow @emilybabay on Twitter.
Contact the Breaking News Desk at 215-854-2443; Follow @phillynews on Twitter.