The cause of the fire, which started on 16 September 2010, has yet to be established and the Health and Safety Executive has been brought in to investigate.
Active operations ceased on Sunday 19 September, but according to the fire service update, a mechanical digger was brought on site the following day when demolition resumed.
A spokeswoman for the fire service said: "The building is so fire damaged and the structure unsound that it will be demolished for safety. We also need it to come down because it is safer then for crews to get in and pull away the debris ensuring no hot spots underneath."
Amcor has come under attack from the Business Sprinkler Alliance, for its failure to prepare for a fire. According to the organisation, only 10% of the building was covered by sprinklers.
Chairman Iain Cox said: "This is a perfect example of how fire can occur at any time, and pose a great risk to the public and its environment. Fire sprinklers can begin suppression within moments, thereby extinguishing it or, at the very least, minimising the production of toxic fumes.
"Had the company involved installed sprinklers to cover its entire property, the building would not have become fully alight. This is a major incident for the fire incident officers involved. Sprinklers would almost have certainly turned the incident into a minor inconvenience and ensured the welfare of the fire service, local communities and environment involved."
