A 911 call was received around 9:30 a.m. from a man at a pay phone about a mile from the campus, said Officer David Hartman, a New Haven Police spokesman.
‘‘All he really said was that his roommate was on his way to the university, to Yale University, to shoot people,’’ he said.
Police later received reports from witnesses who reported seeing someone with a gun, Hartman said. He said that there was nothing specific about the threat and that the call lasted just several seconds.
There were no reports of shots fired or anyone injured.
Police blocked off several streets near the Ivy League university, located in the heart of New Haven. Several local schools also were placed in lockdown.
Yale advised students and staff to shelter in place. The school also issued an advisory asking people off campus to stay away from the area.
The school is on November break, with undergraduate classes to resume Dec. 2. Many students and staff left campus for the Thanksgiving holiday follow Saturday’s traditional football game against Harvard.
Pedestrian traffic in the normally bustling area also was sparse, with cold and windy weather keeping many people inside.
Police in tactical gear entered several buildings, and a helicopter hovered over the area.
Yale has been the target of violence in the past. In May 2003, a bomb damaged an empty classroom and adjacent reading room at the law school.
A Yale professor, David J. Gelernter, was seriously injured in 1993, when a mail bomb mailed by Theodore Kaczynski, the man known as the Unabomber, exploded in his campus office.
Friday’s search came about two weeks after a scare on another Connecticut campus.
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.