The fire, which was limited to a ground floor plant room was extinguished by firefighters.
No injuries were reported.
A spokesperson from Llanelli Town Council said: “There was a fire incident at Llanelly House overnight, the fire was extinguished with no injuries.
“Sincere thanks to the Fire Brigade for their quick intervention.
“Fire damage was limited to a ground floor plant room, the historic parts of the building appear to have been affected by smoke only.
“The House will now be closed for the time being. House Trustees and management are co-ordinating next steps and contacting those with bookings.”
Mid and West Wales Fire and Rescue Service said: “At 12.05am on Sunday, July 9, the Llanelli, Tumble and Gorseinon crews were called to an incident in Llanelly House following the actuation of a smoke alarm.
“Crews responded to a fire confined to a ground floor plant room measuring approximately 4m x 5m within the three-storey building.
“Crews utilised six breathing apparatus sets, one hose reel jet and one thermal imaging camera to extinguish the fire.
“The National Grid were requested to attend to isolate the property’s electrical supply and crews left the scene at 1.49am.”
(Lead image: Carmarthenshire County Council)
