Firefighters have been battling a blaze at a listed 17th century building which has seen more recent use as a swingers' venue.
The two-storey Stratford House in Birmingham, which bears the date 1601 on its front door lintel, suffered damage to its timber roof beams and upper rooms after fire broke out at about 11pm on Monday.
Fire and police investigators have been at the scene but the cause remains unknown.
In January, the Grade-II listed building in Stratford Place was transformed into the Tudor Lounge Club for swingers and adult parties, complete with its own downstairs fetish dungeon.
Fire crews said nobody was inside the building at the time as the private members' club had been closed for the Christmas break.
West Midlands Fire Service, which had 22 firefighters at the scene overnight, said the blaze damaged an upstairs flat and the roof space.
Eve Greenhouse, watch commander, said: "At about 11pm last night four appliances turned out to the fire here with an aerial appliance to tackle a fire in the top section on the first floor.
"Nobody was here, it was closed for Christmas."
She added: "We still don't know the possible causes. Police are helping us with investigations, they are just assisting our fire and research investigation team."
Ms Greenhouse said due to the age of the house, built in the reign of Queen Elizabeth I, firefighters were taking care not to do any further damage.
"It's a beautiful listed building so we're currently liaising with English Heritage to make sure we're not doing anything in terms of when we're clearing up, trying to keep it as intact as possible.
"It's not too bad inside, there's lots of little old nooks and crannies, so hopefully we can salvage as much of it as possible.
"As you can see from the roof we've had to strip a lot of the tiles this morning, just to make it safe."
The structure of the building has been assessed as sound by the fire brigade.