Police were searching Yale University on Monday after receiving reports of a person with a gun on the Ivy League school's campus in New Haven, Connecticut.
The school on its website told students and staff to shelter in place during the search.
"We've notified our community," spokesman Tom Conroy said, adding that warnings about the incident had been sent to students, faculty and staff by e-mail and text.
Televised images showed police officers responding to a largely deserted campus, as most students had gone home prior to the Thanksgiving holiday. New Haven and Connecticut State police responded to the scene, Yale said.
Some 11,250 students attend the prestigious university, located 80 miles northeast of New York City.
Institutions across the United States remain on high alert in the wake of a series of shootings including the attack at Los Angeles International Airport this month where a 22-year-old man killed a security officer and wounded three others, and last year's massacre at a Newtown, Connecticut, grammar school in which a gunman killed 20 young children and six adults.
