A woman has been arrested after a fire ripped through a massage parlour in Adelaide.
The fire broke out at a building housing Siam Retreat Thai Massage and Spa in Vaughan Place in the CBD around 6pm on Wednesday.
Nine fire trucks attended to contain the blaze, which is believed to have begun on the ground floor before moving to the first floor where the parlour is located.
Five people who were inside suffered from smoke inhalation and were taken to Royal Adelaide Hospital for treatment.
SA Police detectives and crime scene investigators later determined the fire was deliberately lit.
A 37-year-old woman was arrested and is being questioned by police.
Other businesses in the heritage-listed building appear to have escaped major damage.