New Haven, Connecticut: Police say they have not found a gunman on Yale University’s campus, and a call warning of an armed man going to shoot up the school appears to be a hoax.

New Haven Police Chief Dean Esserman told a news conference on Monday afternoon that the campus is safe. A lockdown remains in effect on the Old Campus as police search rooms there.

There have been no reports of shots fired or anyone injured, and no arrests have been made.

New Haven police Officer David Hartman says an anonymous caller from a pay phone nearby told them his roommate had a gun and was heading to the campus.

The man who made the call - at 9.48am - did not identify himself and hung up before offering more details, said New Haven Police spokesman Officer David Hartman. New Haven police received the call from a phone booth.

Police and the FBI are investigating whether video surveillance could have captured an image of the caller or anyone else of interest.

At 10.17am, Yale sent out a text alert to the community about the report. Within about an hour of the anonymous call, two witnesses told police they had seen a person with a long gun, Mr Hartman said.

Police are investigating whether those witnesses were looking at law enforcement personnel, Mr Hartman said.

Mr Hartman said a ‘‘basement to roof search’’ of Yale buildings was under way. Multiple SWAT teams were searching the area, he said. Police shut down roads around the Old Campus to traffic and pedestrians and several public schools in the area were put on lockdown as a precaution.