Firefighters entered the building with breathing apparatus and conducted a search but there were no people inside.
No casualties have been reported and the Fire and Rescue Service are checking neighbouring properties and evacuating where required.
An eyewitness told Express that the fire appeared to be in the roof of a property surrounded by scaffold, where tradesmen had earlier been working on.
The next-door property may also have been damaged.
Another eyewitness said that those evacuated had been helped by people from the sports bar opposite.
Pictured: Smoke can be seen rising from a house in the area.
States Police issued an update asking people to avoid the area.
“We are currently dealing with a fire on Mont Le Vaux in the area of St Aubins Village. Please avoid the area whilst emergency services are dealing. Thank you in advance,” officers said.
The main St Aubin road is closed from the top of Mont Les Vaux to Le Haule Hill.
The road also closed at Mont des Longchamps and the Railway Walk is closed at the lower end.
Police are in the process of closing Market Hill.
Sanctuary Trust’s men’s shelter, Sanctuary House, is located next to the property where the fire broke out.
The charity released an update on Facebook confirming that the shelter had been evacuated, and all residents and staff were safe and accounted for.
The social media post read: “We are in the process of arranging emergency accommodation, as we may not be able to return to the property for the time being. It’s too early for us to determine the extent of any damage to the shelter.
“Our thoughts are with our neighbours and we thank the emergency services for their swift action.”
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