150 people were evacuated at the Shoreditch branch of Chariots Roman Spa in the early hours of Sunday morning when the fire took hold.
Six fire engines and around 30 fire fighters were called to the blaze in the four-storey health club on Fairchild Street.
According to the London Fire Brigade, around half of the ground floor was damaged by the fire, with all people evacuating the building unharmed.
The Fire Brigade are currently investigating the cause of the blaze, however, the Metropolitan police spokesperson said:
“We don’t think it’s a crime, therefore we are not treating it as such”.
This is said to be one of the most popular gay saunas in London. A spokesperson from the Waterloo branch of Chariots said: “The Shoreditch branch is currently closed and will not be opened till all rebuilding has been done.”