An investigation is underway after a poster created by a Jewish group at a North Toronto school was “defaced,” the Toronto District School Board said.

A letter regarding the incident was sent home to parents and guardians of students at Northern Secondary School on Thursday. The school is located in the area of Mount Pleasant Road and Eglinton Avenue East.

“I want to share with you a very troubling event that we learned about earlier today,” the letter said. “A poster created by our Northern SS Jewish Club was defaced with anti-Semitic graffiti.”

The letter said the poster was removed from where it was located and police were subsequently contacted.

“This is completely unacceptable and upsetting for all of us at Northern.”

The graffiti drawn on the poster shows multiple swastikas as well as the words "gas 'em all."

In a statement, the Friends of Simon Wiesenthal Center said the school took “swift action” regarding the incident.

“Incidents such as this reveal the ongoing need for tolerance and human rights education inside schools, so it’s encouraging to see the school recognizing this in addition to working with police to find the culprits,” president and CEO Avi Benlolo said in the statement. “FSWC is currently working with the Toronto District School Board to bring its educational workshops to the school in the coming months.”

The school said they will be reviewing security camera footage in the building in an effort to identify who was responsible for this incident.

The school’s letter also urged anyone with information to come forward to assist in the investigation.