After conducting a search for a possible gunman on the campus of Stony Brook University, police have determined there is no immediate threat.

Campus police say at around 1:30 p.m., a man attempted to steal food from a cafeteria at the school. When he was confronted by an employee, investigators say the man showed a gun and fled on foot. He has not been captured.

One student told News 12 Long Island that she saw the cafeteria incident, but didn't see a gun. According to the student, the man didn't have enough money to pay for some of his food, so he took the unpaid items and fled.

The suspect was described as a black man, about 25 years old and wearing a black coat and black wool hat.

Text and voice messages sent to students warned of the situation and instructed them to check the school's Web site for more information, but several students who contacted News 12 Long Island said an alert was not posted until about an hour after the incident began.

Chopper 12 showed students walking freely on campus, and several students said nothing seemed out of the ordinary during the alert. One school official said it is impossible to lock down a campus of 40,000 students.

The school told students to "remain alert, proceed with caution and notify university police if you see anyone fitting the description of the individual or anything unusual."

At around 3:50 p.m., the university posted an update to its Web site stating: "Police have issued an all-clear to continue normal classes and activities."

University and Suffolk County police are continuing increased campus patrols. Police are also examining surveillance video from the cafeteria in the hopes of identifying the suspect.

Gunman emergency alert

Map of Stony Brook University campus