A North York school sent hundreds of students home out of concern for their safety after a suspected graduation prank left the building smeared with cooking oil and peanut butter.

Early Wednesday morning, senior students at Senator O’Connor College School, near Victoria Park Ave. and Lawrence Ave. E., appeared to have spread oil and peanut butter across the floors, stairs and door handles of the high school, a school official said.

The Toronto Catholic District School Board said about two thirds of the 1,200 students were dismissed after the mess was discovered.

“A member of the staff slipped and fell as a result of the prank,” said John Yan, spokesperson for the Toronto Catholic District School Board.

“That is why we acted immediately and closed down parts of the school for the clean up.”

The prank is also a serious safety concern because contact with peanut butter can be life-threatening for staff and students who have allergies, Yan said.

“For those who have attended high school, pranks are a rite of passage, but this one went too far.”

“We know that social media in terms of YouTube and Instagram drives a lot of this wanting to top other schools that are maybe doing the same thing,” he said.

Yan said cleaning crews are working to remove every trace of the substance to ensure the space is safe for those with peanut allergies, which can be potentially fatal.

The pranksters are still at large.

With files from The Canadian Press