DEKALB, Ill. (WLS) -- A bomb threat canceled classes and forced the evacuation of all buildings at Northern Illinois University in DeKalb and three branch campuses Thursday night.School officials said a threat was phoned in shortly before 6 p.m., prompting the school to evacuate all campus buildings in DeKalb. Out of an abundance of caution, officials also closed and searched branch campuses in Hoffman Estates, Naperville and Rockford.NIU officials said the threat appears to be a hoax and "one of a series of bogus bomb threats" called into colleges and universities across the region. However, police are continuing to search each building before anyone is allowed back in.Alerts posted online directed anyone on campus to stay 500 feet from campus buildings and report to the Convocation Center, the first building to be swept and cleared."I just haven't been able to get back into my room, but the word around is that people have been able to get back in their rooms. So hopefully, after this I'm able to get back and get some of my things and make sure everyone on my floor is OK, too," said Jeremy Pope, an NIU student.Two more buildings in DeKalb, Grant North residence hall and the Holmes Student Center, have since been cleared and reopened. Buses were provided to take students from the Convocation Center to the cleared buildings."We're waiting for the residence halls to be cleared. Those students who live off-campus have been notified that they can return to their homes and apartments off-campus," said Brad Hoey, NIU spokesperson.Just before 9 p.m., both the Hoffman Estates and Naperville campuses were cleared but will remain closed for the night, officials said.All NIU classes and events were canceled Thursday night, with the exception of an NIU basketball event, which was held as scheduled in the Convocation Center.A similar threat was investigated at DePaul University's O'Hare campus Thursday night. Two floors of a building were evacuated for a short time, but classes resumed after a police search found nothing suspicious.