York Regional Police are investigating after anti-Semitic graffiti appeared on the exterior of a school in Vaughan this week.

An image of a swastika painted on a brick wall in place of what looked like a Canadian flag was circulated in a press release by Jewish advocacy group B'nai Brith Friday. The organization called the messages "appalling."

Scrawled on another exterior wall was what appeared to be two towers with the words "Jews did 911" overtop.

York Regional Police said Friday the incident took place Wednesday night at Woodbridge College High School and the graffiti was discovered Thursday morning ahead of a graduation ceremony. Officers at the scene checked for video surveillance and school staff scrubbed the graffiti away, Staff Sgt. Darrin Leitch told CBC Toronto.

No suspects have been identified and the incident has been flagged to the force's Hate Crimes Unit, Leitch said.

In its release, B'nai Brith said it learned of the graffiti from a caller who phoned its 24/7 anti-hate hotline and sent in photos. The organization also said it commended York Regional Police for the force's swift response.

"This disgusting act of antisemitism and racism could have spoiled a graduation ceremony at the school, right before Canada's 150th birthday," Michael Mostyn said in the release, "but York Regional Police ensured that the events would go on smoothly without any trace of the loathsome vandalism that took place."