One person, thought to be a man, is now understood to have died in the blaze in a Lerwick house early on Sunday morning.
The Scottish Fire and Rescue Service had earlier stated that a woman had been removed from the two-storey building in Burns Lane and taken to the Gilbert Bain Hospital in Lerwick.
Four fire appliances were called out around midnight on Saturday after the fire broke out in the building.
According to the fire service a call was received at 11.59pm and initially two appliances were sent to the scene. However, assistance was asked for and another two engines were despatched.
Four sets of breathing apparatus were used, along with two hose reel jets, and the fire was extinguished by 3am.
An area surrounding the fire has been cordoned off and a specialist investigation team is believed to be heading up from the mainland.