PRINCE.EDWARD.ISLAND (CBC) - Charlottetown Rural High School operated under heightened security Wednesday, a day after a shooting threat appeared on Facebook.

Although the school was locked down, according to police, classes continued as usual.

"To find out about something like this last night and have to come to school, it's just really really nerve-racking," said Ashley Shoemaker, a student at the school.

All doors were locked, except the front door, which was guarded by uniformed police officers. Other officers patrolled the grounds and the school building.

Police first heard about the threat in a complaint from a student at 9:30 p.m. Tuesday.

"There was a posting that come up on Facebook and all it said was, 'There will be a shooting tomorrow at chtn rural high school' and 'hide.' And that was the only person then the person disappeared," said Charlottetown police Sgt. Mike Quinn.

In following up the complaint, police found the posting appeared at 9 a.m.

Deputy chief Gary McGuigan said an investigation is underway to identify the Facebook user and where the message originated.

"As people know with Facebook, it could have come from outside the province or even outside the country," he said.

The school was contacted and officials decided to keep the school open and proceed with heightened security.

"The threat, as far as we know at this time, appears to have been made by a fictitious character and it is not a threat against any specific person or persons," said Ricky Hood, transitions co-ordinator with the Eastern School District.

"With that level of information, and gathering what we could from the city police, it was agreed that we would try to have an operation at the school as normal as possible. We do believe the school is a safe environment for students and staff."

The principal briefed staff on the situation before classes started and then addressed students in their homerooms and provided all the information that was available.

"There was very little commotion at the time the information was passed on to the students. The bell rang and the vast majority of students moved on to their first class," said Hood.

Emily Shoemaker, a student at the school, said her parents thought school administrators should have taken further action.

"I'm kinda upset that they didn't. Parents are very upset with the school board that they didn't," she said.

Another student, Josh Misener, said he felt uncomfortable being at the school.

"I really didn't want to stick around when I found out what was going on," he said.

Officials said there will be no further police presence at the high school because there are no classes for the next two days due to a scheduled teachers' conference.