NEW : Northern Michigan University officials say situation is under control . Officials continue to warn students and faculty not to wander on university grounds . The public school system has more than 3,000 students and 400 staff members , she said . Police put the campus on lockdown early Wednesday because of threat against students , others . Public schools in Detroit were also closed , the interim superintendent said .
NEW : Northern Michigan University officials say situation is under control . Officials continue to warn students and faculty not to wander on university grounds . Police put the campus on lockdown early Wednesday because of threat against students , others . Public schools in Detroit were also closed , the interim superintendent said .