A lockdown at Winslow Township High School is over, and students have been dismissed for the day, but the investigation into whether an armed man entered the building today continues.

The school, which was the target of a foiled guns-and-terror plot last year, was under lockdown for several hours while authorities searched the building.

Shortly after noon today, a Winslow police officer assigned to the school received a report that there was a man with a gun in the building. The officer quickly secured the building and called for assistance. Students were kept in their classrooms, past normal dismissal time, while a search was conducted.

No weapon or suspect was located, and no one was injured, Bill Shralow, a spokesman for the Camden County Prosecutor's office, said in a release.

Last year, authorities thwarted an attempted shooting plot at the Camden County school.

Four youths allegedly hatched a plan to gun down students, teachers, and others inside the school and nearby.

The boys made arrangements to purchase weapons and allegedly planned to start a food fight in the Winslow High cafeteria during a fourth-period lunch. They would then use that incident to start throwing chairs and executing people at will, according to authorities.

The youths compiled a hit list of about 25 people.

Three of the teenagers involved in the plot were sentenced to time in state prison or juvenile detention. A fourth boy, who was said to have minimal involvement in the plan, received probation.

Contact reporter Kristen Graham at 215-854-5146 or kgraham@phillynews.com.