After the report came in, the university had urged students and staff to stay inside, and several police officers responded to the West Haven school. The university said that police were still searching buildings Tuesday afternoon and that the main campus was still under lockdown while restrictions were lifted for its north and south campuses.
Kyle Gelinas, an 18-year-old freshman, said he saw a person in handcuffs being questioned by police across the street from his dorm.
"He's just sitting on the railing. They're just talking to him like a casual conversation," Gelinas said. "Everything is very calm."
The university enrolls about 6,400 students. The majority of its 4,600 undergraduates live in university housing.
Several nearby public schools also put out shelter-in-place orders as a precaution.
No further information was immediately available.
The incident marks the third scare at a Connecticut university in the last month.
Last week, Yale University in neighboring New Haven was locked down for six hours after a man called police and said somebody was coming to shoot up the campus. Police have said that appeared to be a hoax.
Central Connecticut State University was in lockdown for several hours Nov. 4 after reports by witnesses of a masked man carrying a gun or sword. Police arrested a student, David Kyem, who said he had been wearing a ninja-like Halloween costume and meant no harm. He faces charges including breach of peace.