A firefighter is in a critical condition following a blaze at the former Jenners department store building in Edinburgh city centre.
The Scottish Fire and Rescue Service (SFRS) said five firefighters have been taken to hospital for treatment with one apparently fighting for their life.
The families of all those affected have been made aware.
Emergency crews were alerted to the "very serious and complex incident" in the city's Rose Street shortly before 11.30am on Monday.
SFRS said 22 appliances were mobilised to tackle the flames. In an update later on, a chief officer said 11 appliances and other specialist resources remain in attendance.
On arrival, firefighters found the iconic building "well alight".
Pictures and video taken at the scene showed smoke billowing from the category A-listed building.
Marks & Spencer and the Mercure Hotel, in Princes Street, have been closed as firefighters work in the area, and some buildings have been evacuated.
South St David Street and a number of surrounding roads have been closed to traffic and pedestrians in the meantime.
Lothian Buses also warned that due to the incident, some of its services were being diverted.
A Police Scotland spokesperson said: "Please avoid the area if possible and follow directions regarding alternative routes."
Ross Haggart, interim chief officer with SFRS, said: "The fire at the Jenners building in Edinburgh is a very serious and complex incident and regrettably I can confirm that five of our colleagues have been taken to hospital for treatment and one remains in a critical condition.
"The families of all those affected have been made aware.
"We currently remain at the scene with a total of 11 appliances and other specialist resources in attendance."
The building, which Jenners moved into in 1895, is one of the best known in the capital.
The closure of the store, which was then controlled by Mike Ashley's Frasers Group, was announced in 2021.
Renovations are ongoing to transform it into a hotel, supported by a firm owned by fashion billionaire Anders Holch Povlsen.