Police locked down Central Technical School on Thursday afternoon as they sought to secure the area after gunshots were reported. (Patrick Morrell/CBC)

Police have arrested three boys after reports of gunshots in a central Toronto high school forced the school into lockdown mode for several hours.

Toronto police responded to a report of gunfire at around 1 p.m. at Central Technical School, at the intersection of Bathurst and Harbord streets.

No one was hurt in the incident. Police found one shell casing in a stairwell, said Const. Wendy Drummond.

Toronto police said they arrested two people on school property, while the third person was picked up by officers on Thursday evening. Police have not said if charges will be laid.

A lockdown that went into effect shortly before 2 p.m. was lifted at around 4:45 p.m. Students who were in the school at the time of the shooting had to stay where they were when the lockdown was called.

By around 5:15 p.m., all students were allowed to leave the school.

"We were just sitting in the library and [were] bored out of our minds," student Kevin Almeida said as he left the school. "They wouldn't tell us what was happening. We have to figure [it] out through texts and calls from our friends."

Police deployed canine units and an emergency task force to sweep the school before allowing students to leave.

They also set up a command post on Borden Street, just east of Bathurst Street. Stretches of Borden and Harbord streets were closed to pedestrians and vehicles. Police were advising concerned parents to call the school, but said they would not be allowed into the building.

Police had also ordered a "hold and secure" designation at two other nearby schools, Harbord Collegiate and King Edward Public School. That order was lifted just before 4 p.m.

Under that designation, students and teachers in the school can carry on as normal, but all doors and windows are locked and no one is allowed in or out of the building.

With files from The Canadian Press