UPDATE : Hamilton police say vandals who smashed shop windows planned ahead

Police say the masked vandals who caused up to $100,000 in damage in Hamilton Saturday night were organized and likely planned their actions ahead of time.

Insp. Paul Hamilton says officers are reviewing witness statements and video of the incident, in which around 30 people hurled rocks through shop windows on a busy city street.

Hamilton says members of the group carried a banner that read, ``We are the ungovernables.''

He says the vandals displayed tactics commonly seen at major demonstrations, including wearing multiple layers of clothing that can be peeled off to quickly change their appearance as they flee.

Hamilton called on witnesses, and even the vandals themselves, to come forward with information.

He says an event billed as the Southern Ontario Anarchist Bookfair took place in downtown Hamilton over the weekend, but so far there is no definitive link between it and the damage done.