Following a Sunday night bomb threat, and a localized evacuation effort, UNC’s campus was given the “all clear” signal today at 5 a.m., according to the university.

At approximately 9 p.m. Sunday night, Orange County 911 received a call from a male saying he had an explosive device near the central “Pit” area of campus. UNC police, aided by the Orange County Sheriff’s Department, Chapel Hill police and the State Bureau of Investigation, responded by evacuating nearby buildings, setting up barrackades and conducting bomb-squad searches. However, the Daily Tar Heel reports that two hours lapsed before news of the threat was posted to the university’s Alert Carolina Web site, and nearly three hours before a text message was sent to alert-message subscribers, at approximately 11:45 p.m. The newspaper also reports that “students in the [Student] Union’s gallery and Yackety Yak offices were not evacuated until Daily Tar Heel staff informed them of the threat.” The UNC Student Union, which houses the DTH newsroom, is adjacent to the Pit.

In its 5 a.m. press release, announcing the “all clear” signal, the university explains its reasons for evacuating the area first, before sending out any alert messages. (After the jump.)

Police and University officials emphasized that the most important priority initially was for law-enforcement agencies to respond to the immediate situation and to take those steps necessary to protect students and the rest of the campus community.

After the area was secure, University officials turned their attention to communicating with the campus. Even though the Pit area had been secured, the University sent a text message (!Alert Carolina! UNC Public Safety is investigating a bomb threat near the Pit. Go to alertcarolina.unc.edu for updates.) to all students, faculty and staff who have registered their text message-capable cell phone in the online campus directory.

Later today, UNC issued another release, responding to “some questions about the University’s protocol for use of our siren system and text messaging.” The post emphasizes UNC’s reasons for not deploying a siren–insisting the bomb threat did not fall under one of three scenarios of “imminent threat” that would permit a siren (an armed person on or near campus, a major chemical spill or hazard, or a tornado)–and added of the late Alert Carolina message:

In all cases, the University focuses first on responding to the threat and protecting those directly at risk. Once that essential work is done, and when the facts are available, we will post information about campus security to the Alert Carolina Web site.

The DTH, quoting UNC Department of Public Safety spokesman Randy Young, reports the investigation is ongoing. More updates to follow.

Note: A correction has been added to the timeline.