The thousands of students who live on the Louisiana State University campus have begun returning to their dormitories after bomb-sniffing dogs and police methodically swept residential halls Monday following a threat that sparked a campus-wide evacuation.

LSU spokesman Herb Vincent said officials hope to reopen the Baton Rouge campus by Monday night, but they aren't certain if a building-by-building sweep will be complete before Tuesday.

"Residential Life buildings have now been deemed ready to return to normal operations," Vincent said Monday evening.

Evangeline Hall, a residential building on campus, was reopened first and officials began directing some of the 6,000 on-campus residents into the building as the investigation continued, Vincent said. He said residential halls were searched first and buses to and from the campus have been running normally.

Thousands of students, professors and workers were told to leave campus Monday morning after a threat was phoned into 911 about 10:32 a.m., university spokeswoman Kristine Calongne said. But the threat did not indicate a specific part of campus, so police and bomb-sniffing dogs have been meticulously sweeping each of the 250 buildings on campus.

"Please evacuate as calmly and quickly as possible," a statement read on the school's website.

LSU Police Capt. Corey Lalonde said no explosives have been found.

By mid-afternoon, the LSU campus was largely deserted and roads were closed, though some people and cars were still moving around. Police officers with dogs combed through buildings, including the computer services center.

Bomb threats were also made last week at the University of Texas at Austin, North Dakota State University at Fargo, and Hiram College in Ohio.

"It's kind of been an epidemic. This has been the fourth in a week. But it's better to be safe than sorry," Joseph Vera, a communications disorders graduate student, told the Associated Press.

Vera and a fellow graduate student were working in a language clinic with seven children near the edge of campus when they received the text message about the bomb threat. The pair walked the children across the street to an off-campus restaurant and they called the children's parents.

Capt. Doug Cain of the Louisiana State Police told the Associated Press that bomb technicians were on the scene and police were working with departments in other states to determine whether the bomb threats are related.

No specific location for the LSU has been identified and parish 911 had been called, the school said in a press release.

Classes at the school were canceled, the Houston Chronicle reported.

“I was in the middle of taking a test and they walked in and told us we had to leave campus,” Andrew Arceneaux, an LSU student, told The Advocate.

Around 30,000 students and faculty attend LSU.

Traffic getting out of the campus was in a gridlock, as students sat in buses at a standstill, The Advocate reported. Still, the campus was evacuated in under an hour.

LSU System President William Jenkins told the newspaper that he readied the school's emergency response systems after learning about the bomb threat.

“We hope it’s a hoax, but we can’t take that chance," he said.

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The Associated Press contributed to this report.