A male suspect has been arrested following an alleged threat posted online involving a Metro Vancouver high school.

Richmond Mounties said a youth was arrested at Robert Alexander McMath Secondary School on Tuesday, but would not say whether he is a student at the school. The suspect's age has not yet been provided, and investigators said he was not known to police prior to the incident.

The arrest was made in connection with the alleged threat, police said, but they have not confirmed what the threat actually was.

A student showed CTV News an online message he said had been circulating on social media that referenced the possibility of a shooting, but investigators would not confirm any details.

The RCMP said the investigation began Monday when the names of the school's Wi-Fi networks were changed. From there, the situation escalated to a "series of threats directed towards the school," the RCMP said.

The school sent letters home to parents following the Wi-Fi incident, telling them it was safe to send their children back to school on Tuesday. Some students stayed home to be safe, but some of those who went back to school were surprised that they ended up having to stay inside classrooms for most of the day.

Mounties said the school was put in to a hold-and-secure Tuesday morning investigators were dispatched to the grounds to respond to the threat. Those inside told CTV that officers searched lockers and checked phones as they swept the school.

"It's shocking because you don't expect it to happen in your school," said Marion Thomas, a parent whose teenage son was among the students held inside a classroom all day.

"The RCMP searched every bag on every student searching for something," she said.

Students and staff remained indoors until 2:30 p.m., when RCMP said the threat had been "resolved." Students were then dismissed.

Cpl. Dennis Hwang said all reports of threats to students and staff are taken seriously, and that they'd worked alongside the Richmond School District to conduct a safety assessment.

Police have not said what charges, if any, the youth taken into custody could face.

With files from CTV Vancouver’s Maria Weisgarber