STANFORD - Students and faculty members at Olympia Middle and High School were locked in classrooms and the cafeteria throughout Wednesday afternoon because of a threat found on a restroom wall that morning.

Olympia Superintendent Donald Hahn said the writing, which indicated there was a firearm in the school, was found in a men's restroom about 11:40 a.m. The lockdown was announced about 11:45 a.m., he said, and students were dismissed from school at their scheduled time.

About 20 county and state police officers were at the school Wednesday to investigate the threat and search students, their bags and lockers, police said. Police remained in the building until after students were dismissed for the day.

Nothing illegal was found, but McLean County Sheriff David Owens said officers took the threat seriously. They kept students from leaving to keep them safe and to let police try to find out who was behind the threat.

He said officers will be at the school again today, and the need for a police presence would be evaluated on a daily basis.

Owens said the threat was "general in nature" and was likely a copycat incident of threats in East Peoria. But police had no choice but to investigate, he said.

"The day and age we don't take a threat seriously is gone," Owens said.

A threatening note was found in a restroom at East Peoria High School on Tuesday, and another was found in restroom at East Peoria's Central Junior High School on Wednesday, WEEK-TV reported.

Hahn said 900 students in Olympia's high school and middle school were locked into classrooms and were told to go to corners of the rooms, where they could not be seen through glass in the doors.

He said the threat's timing was inconvenient because 300 students were in the cafeteria, and those students remained there during the lockdown.

"We were not able to determine who did it yet, but that investigation is going on," Hahn said.

Several sets of parents stood just outside the school Wednesday afternoon, and some were angry they could not take their children home.

Julie Shindel, of Minier, said she didn't understand how she could be denied a chance to take home her 12-year-old daughter, Nicole. The girl's grandmother, Deanna Sanders, said recent school shootings elsewhere in the country have caused panic in her and many other parents.

"There's been a chain of ludicrous events in other states, and now it's like it's our turn," Sanders said.

Tammy Webb, of Stanford, said she came to the school after her daughter sent a text message about the lockdown to Webb's cell phone. Webb said she had two daughters in the building, and she said it wasn't right that she was not allowed to remove them from the building.

A state trooper exchanged words with a woman near the school's front door, and he held up handcuffs and threatened to arrest her unless she moved from the front of the building.

Another Illinois State Police official, Lt. Ted Kerrn, later talked to parents outside the building and said he understood their concerns, but the children needed to remain locked down for their safety and so police could determine who was responsible. And he said police could not allow students to roam free with the possibility one had a weapon.

Zach Thomas, a freshman from Stanford, said after the lockdown that school officials didn't give students any details about the threat, and it was nerve wracking for some with him in the cafeteria. He said groups of students were brought to a gymnasium and patted down for weapons.

Hahn said students and staff members were not given details on the threat as police searched the school. But he said school officials will tell students as much as they can this morning and encourage those with information to come forward.

Bailey Peasley, a sophomore from Bloomington, said she was brought into an office and asked to say who was in the hallway when she arrived. And she said police asked her for a handwriting sample.

Though the searches didn't turn up anything related to the threat, Sheriff's Lt. Jeff Elston said one piece of contraband was confiscated. He said the contraband was not a weapon and was not illegal, but it violated school policies.

Elston declined to say what the item or material was.

Hahn said school administrators had reevaluated emergency plans because of recent school shootings elsewhere in the country, and the high school staff met on crisis planning before school the same morning of the threat. He said he hopes employees at his and other schools would learn from the threat and the reaction.

Elston encouraged anyone with information to call the McLean County Sheriff's Office at (309) 888-5019.