Six students from a prestigious private all-boys Catholic school in Toronto have been arrested and charged after a video showing an alleged sexual assault by members of the school’s football team was posted on the internet.

The students from Saint Michael’s College were charged on Monday with assault, gang sexual assault and sexual assault with a weapon.

The arrests came amid a growing scandal over violent “hazing” rituals at St Michael’s – a private Catholic school which counts high-ranking politicians in both Canada and the United States among its alumni.

The school received a bomb threat on Monday morning, just as the students were set to appear in court.

Videos of the locker room incident first started to circulate last week, but the Toronto police inspector Dominic Sinopoli said on Monday that the school failed to notify police, who first learned of the alleged assault from news reports.

Eight students were expelled or suspended in relation to the video, which allegedly shows members of the school’s football team sexually assaulting a fellow student with a broom handle.

On Monday, five students turned themselves in to police and one was arrested on his way to school. Police have called for any other victims to come forward.

“We have reason to believe there are more incidents and more videos,” said Sinopoli, head of the Toronto police’s sex crimes unit.

Sinopoli told reporters he was concerned that the graphic video of the assault remained online. Last week, police advised anyone sharing the video that they could face charges for possessing and distributing child abuse images.

Following the announcement by police, the school issued a statement supporting of the charges. “We believe charges are absolutely appropriate in these circumstances,” the school said.

“The incidents of sexualized assault that happened to our students and on our school grounds are simply horrific,” the school said.

“These incidents are clearly indicative we have a problem. We need to do much better at our culture and our students’ ability to talk to us.”

The school’s principal, Greg Reeves, has come under severe criticism for failing to immediately report the assault to police, after he received a copy of the video on 12 November.

It wasn’t until later in the week – when reporters contacted Toronto police for comment – that officers learned of the crime.

In an interview with the Globe and Mail, Reeves said he had wanted to speak to the victim’s family first, before contacting police. “I had set up four expulsion meetings [the following] morning, and at that point I couldn’t deal with that video,” he said.

On Sunday, the school said it was conducting an independent examination into the “underlying attitudes and behaviors” that it said were inconsistent with the school’s culture.