A pig's head was found outside the front entrance of the Montreal Police Brotherhood headquarters on Friday morning, along with a human form made out of tree branches set against the front door.

Montreal police are investigating it as a case of vandalism. The union office is located on Gilford Street in the city's Plateau neighbourhood.

A note was also attached to the door, including a possible reference to what protesters in Mexico chanted last fall in support of kidnapped students.

Officers cordoned off the area Friday morning and removed the signs of evidence. A city worker was seen carting away the pig's head.

The police brotherhood declined a request for an interview, but said it hadn't received any threats recently.