Seven McDonald's restaurants in and around Montreal, Canada have been vandalised in simultaneous attacks.
The attacks all took place early in the morning. In all incidents, rubbish bins were set on fire in the toilets.
Police are investigating whether the attacks were linked to a dispute between McDonald's and the trade union, Centrale Syndicats Nationaux.
Union spokesman Mr Marc Laviolette has denied any connection to the vandalism, calling the damage "regrettable".
Last month, the sole McDonald's branch in Canada with union workers was closed.
The union accuses the restaurant management of systematic union-busting.
