BATON ROUGE, La. — Thousands of students, professors and workers were evacuated from Louisiana State University’s main campus Monday following a bomb threat, school officials said.

The evacuation was prompted by a threat phoned into 911 about 10:32 a.m., university spokeswoman Kristine Calongne said. The caller didn’t direct the threat to any specific area of the campus.

The university issued a statement on its website announcing the evacuation an hour later, then distributed the information through text messages, emails and social media.

“A bomb threat has been reported on the LSU campus,” the statement said. “Please evacuate as calmly and quickly as possible.”

There are 30,000 students, professors and university employees on the Baton Rouge campus, but it was not clear how many were present at the time of the threat.

“Monday ... is a very big class day, so I think the majority of that group was probably on campus at the time,” Calongne said.

By mid-afternoon, the LSU campus was largely deserted and roads were closed, though some people and cars were still moving about campus.

The university sent a follow-up message to students at 1:36 p.m. telling them not to return.

“LSU continues to investigate the bomb threat reported earlier today. Please stay off campus unless directed to return,” the message said.