A bulldozer is already in place behind the temporary hoarding at Octopus restaurant, to begin taking the fire-damaged structure down.
Octopus, at Havelet in St Peter Port, burnt down on Saturday 24 February.
It was one of the most serious fires in Guernsey in years, and took firefighters around 12 hours to put out and a full day to ensure everything was dampened down.
The blaze led to the partial collapse of the roof.
Days later, Octopus was fenced off to prevent people getting in.
The building's insurance broker, Network, has used social media to urge people to keep away, as demolition begins today, 19 June.
It says part of the roof dates back to the old Half Moon Cafe and the slates were known to contain hazardous materials, although many have been removed, where possible, pre demolition.
But, Network says there is bound to be dust and that may contain contaminants.
It says the contractor has liaised with the Health and Safety Executive and everyone working on site will be wearing protective clothing.
Demolition will be phased over eight weeks and air monitoring will take place during the initial period.
Restaurant owners Mike and Delphine Pesrin have said they do intend to rebuild and reopen the bar and grill.
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