Image copyright Getty Images Image caption Police were called out to St Michaels College School after a bomb threat was received

Six teenage boys from an elite school have been charged with gang sexual assault after videos of alleged hazing incidents surfaced online.

St Michael's College School, a private Catholic all-boys school in Toronto, expelled eight students last week in connection with the incidents.

Police say they are investigating at least four separate assaults, two of which were sexual in nature.

The school has been accused of turning a blind eye to hazing and bullying.

The school received a bomb threat on Monday morning, just as police were giving a press conference on their investigation.

Six teenage boys have been charged with assault, gang sex assault and sex assault with a weapon. Their identities have been withheld because they are minors.

Canadian media first reported on the expulsions last week.

CityNews says it saw two videos of alleged hazing incidents. In one of the videos, a male student is naked from the waist down in a locker room, and appears to be sexually assaulted with a broom handle.

In another video, a male student sits in a bathroom sink in his underwear, while other students slap him and splash him with water, CityNews reported.

Police say the videos meet the definition of child pornography.

Dominic Sinopoli, who heads Toronto police's sex crimes unit, told media on Monday anyone in possession of the video should "delete it".

Mr Sinopoli says he believes there are more videos and more victims, and is urging people to come forward if they have additional information.

Meanwhile, St Michael's is initiating an independent investigation into the incidents.

"We want to come out of this as leaders in understanding how to frame a culture so this doesn't occur," principal Greg Reeves told CBC News.

Mr Reeves described the contents of the videos as "horrific".

The school has come under fire for not reporting the incident to police sooner, and trying to deal with the allegations internally.

St Michael's became aware of the locker room video on the evening of 12 November, but did not bring it to police attention until two days later, after media began reporting on it.

Toronto police detective Dominic Sinopoli told media that police are investigating whether the school fulfilled its legal obligation to report the incident to police.