School officials say the increased security comes because a student found a threat written on a classroom desk on Monday. It threatened violence on the campus on Thursday.
"We are checking at the entrance all the IDs of all the people coming in to make sure they belong on our University," said Paul Cell, the university police chief.
Police are still trying to track the source of the threat, and further details weren't disclosed.
School spokeswoman Minne Ho says campus security was increased Thursday as a precaution. A dozen or so officers are usually on campus daily, but there were be 70 to 100 on Thursday, as area police departments sent in officers.
"It is in the best interest of our students and our campus not to give any single immature or disgruntled individual the power to shut down New Jersey's second largest university, at any time," school president Susan Cole said.
Students and staff received e-mail and cell phone text message alerts from the school about the situation.
This is the public safety advisory that went out to students:
"The University has received a threat against the campus community timed for Thursday, April 10, 2008. On Monday evening, April 7, 2008, the University Police received a report of a message written on a desk in Dickson Hall threatening the safety of the campus. Since that time, this matter has been under active and intensive investigation by University Police. At this point, there is no evidence to confirm that the threat is credible, nor can it yet be dismissed as a prank."
Police continue to investigate who scribbled that note.
