Crews from Scalloway, Lerwick and Bixter attended the blaze at the property in Tingwall following a 999 call to the Scottish Fire and Rescue Service (SFRS) made shortly before 3.20am.
With a person unaccounted for, eight firefighters worked inside the burning building wearing breathing apparatus and equipped with four main jets.
They conducted a search but found no-one inside the property and information from a member of the public later indicated the home is likely to have been unoccupied.
Station Manager Myles Murray, the incident commander, said: “This was a significant fire that resulted in severe damage including the collapse of the building’s roof.
“Due to the extent of the damage our crews have as yet been unable to access every part of the structure, which is obviously required to confirm no-one was present.
“Internal and external firefighting operations brought the flames under control by 5.30am but dampening down work has continued throughout the morning.”
He added that SFRS officers will work to establish the cause of the incident.
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However, he said there are practical steps everyone can take to reduce the chance of a fire happening in their home.
The ongoing Join Scotland’s Fight Against Fire campaign calls on people to understand the common causes of fire and take simple steps to address them.
The campaign advises householders not to overload electrical sockets, place candles near items that could easily catch fire, or walk away from a cooker without first taking pots and pans off the heat and switching the dials off.
Station Manager Murray said: “Our crews regularly provide free home fire safety visits to help householders stay safe, so I would urge anyone who thinks they could benefit to get in touch with us.
“We also want people to consider the safety of their friends, family members and neighbours.
“If you know someone who could be at increased risk then put them in contact with the fire service so we can provide support – it really could prevent a tragedy.”
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