A loaded handgun was found inside a knapsack at an east Toronto high school on Wednesday, a startling discovery that police say has led to charges against four students.

Toronto police are still investigating, but Const. Tony Vella said that three male students and one female student at Blessed Mother Teresa Catholic Secondary School,  40 Sewells Rd., near McLevin Avenue and Neilson Road, are facing charges, including possession of a handgun.

Vella said that police received a tip from Crime Stoppers before making arrests just before 2 p.m.

The school was temporarily placed under a hold-and-secure order, but that was later lifted.

John Yan, the head of communications for the Toronto Catholic District School Board, said the hold-and-secure order was lifted at approximately 3:30 p.m., the end of school day.

He confirmed that "four students were taken into custody as a result of the investigation."

Yan said a voicemail has been sent to inform parents about the incident.

With files from The Canadian Press