Guests were evacuated from a hostel after a fire broke out in one of the rooms.
The emergency services were called out to reports of a serious building fire at Merchants Terrace, on London Road in King's Lynn at about 9am on Monday.
Four appliances from King's Lynn and Terrington were called to the scene and used breathing masks to enter the building.
Station manager at King's Lynn Terry Pinto said: "This morning we were called to a serious fire at a property where everyone has been evacuated safely.
"The initial crews worked really hard on the building to contain the fire and stop it spreading into other bedrooms.
"The main building has been left unharmed and the residents can go back in."
Police also attended.
The accommodation run by Notting Hill Genesis provides supported housing for single homeless people.
There are currently 18 people living in the building.
A Notting Hill Genesis spokesman said: "As soon as the fire alarm went off staff were aware. They found the smoke coming out from under the door of the affected property and alerted the emergency services immediately.
"The bedsit has been sealed off and is uninhabitable.
"The rest of that floor is being vacated for the next 24 hours.
"Alternative accommodation has been offered to everyone living on that floor.
"Thankfully no-one was injured in this incident and we are grateful to the quick response of our staff at Merchant Terrace and the fire brigade for ensuring the safety of our residents.
"Investigations into the fire are ongoing."
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