(CNN) -- Northern Michigan University officials say the situation "is under control" after a telephone threat against students, faculty and others prompted a lockdown of the Marquette, Michigan, campus Wednesday morning.

However officials continued to urge students to remain in their dormitories and visitors to stay away from the campus until further notice.

The administration closed the university at 8:20 a.m. Wednesday after campus police learned of a telephone caller who had earlier threatened to attack NMU.

Cindy Paavola, the university's director of community relations, said campus police took the threat seriously, thus prompting the administration to close the university as a precautionary measure.

"The caller threatened that there would be harm to students, faculty, staff and administrators," Paavola said. "They didn't identify particular people, but it was a wide-ranging threat and we are taking it seriously."

"We don't know the seriousness of the threat because we haven't caught up with this person. Rather than be sorry, we're going to be safe," Paavola said.

State and local law enforcement authorities are assisting university police in the investigation, she added.

The Marquette Area Public Schools also sent students and staff home, interim superintendent Debra Veiht told CNN.

She said police referred to a threat on a blog, which they deemed credible.

"We put in our emergency plan into place and it's running smoothly," Veiht said.

The public school system has more than 3,000 students and 400 staff members, she said.

The Marquette Senior High School is located about a half-block away from the university.

University officials locked down all buildings so no one could enter or leave, and told students living on campus to stay in their dormitories. Paavola said several office buildings were evacuated Wednesday morning.

CNN's Chris Kokenes contributed to this report