A Louisville high school was placed on lockdown Wednesday after police received a call warning that someone with a gun was in the school.

Police went room to room at Fern Creek Traditional High School and were interviewing potential witnesses, but no one had been found with a gun at the school, Louisville police spokesman Phil Russell said.

Police helicopters hovered over the school, which has more than 1,200 students. TV video showed a police officer with a dog searching cars in the school parking lot.

Several dozen parents gathered outside the school. Some received text messages from their children who said they were locked in their classrooms with the lights out.

The lockdown was prompted by a student who thought she saw a young man with a weapon talking to two others in the school cafeteria, said Jefferson County public schools spokeswoman Lauren Roberts.

Roberts said the student didn't recognize the young man.

A nearby elementary school also placed on lockdown as a precaution.