NEW HAVEN, Conn. — An anonymous caller warned authorities today that his roommate was on his way to Yale University to shoot people, leading officials to lock the Ivy League campus down as police searched for a gunman. At least two witnesses reported seeing someone on or near campus with a long gun.

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 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.

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.

By The Associated Press