A major blaze has broken out at the Primark store in Belfast city centre.
Shoppers and staff were evacuated from the historic five-storey building at around 11am on Tuesday.
Huge plumes of black smoke and flames could be seen coming from the roof of the Bank Buildings, which is home to the newly-refurbished Primark store.
The building is “at risk of imminent collapse”, a police officer at the scene told the BBC.
Primark chief executive Paul Marchant said he is deeply shocked and saddened by the fire that has destroyed the Belfast flagship store.
He reassured staff who worked in the building that he will ensure they are “fully supported”.
Marchant also said he will work with the authorities and building contractors to establish the cause of the blaze that destroyed the five-storey building.
Michael Graham, assistant chief fire and rescue officer, said his crews had been battling the blaze for six hours.
Graham said: “It has been a long and arduous six hours for them but we will continue to fight the fire until we extinguish it.
“It is one of the biggest we have experienced in the last two to three years.”
He said he was concerned about the front and two sides of the structure.
He added that he did not yet know what caused the blaze, nor whether there were fire alarms or sprinklers in place.
In a statement, a spokeswoman for the Northern Ireland Fire and Rescue Service (NIFRS) earlier said: “NIFRS received a call at 11am today to a fire on the top floor of the Primark building – a five-storey commercial property in the Castle Street area of Belfast.
“Eleven appliances are in attendance. The building has been evacuated.
“The public are advised to avoid the Castle Street/Royal Avenue area whilst the incident is ongoing.”
The force added that the incident was likely to continue “throughout the day” and advised residents and businesses to keep their windows and doors closed. There are 80 fire fighters battling the blaze.
The Police Service of Northern Ireland also issued a warning to motorists to avoid the area.
A number of diversions are in place at Bridge Street, High Street, Castle Street and Queen’s Street as well as Royal Avenue and North Street to allow the fire service to deal with the ongoing incident.
Police have advised drivers to seek an alternative route.
There were no initial reports of injuries, but that has yet to be confirmed by the authorities.
One witness said he spotted smoke coming from the roof of the building and alerted the security guards inside the store.
The man, who asked to remain anonymous, said it appeared that the security guards were not aware of the fire. He also claimed he could not hear any alarms alerting the staff and public.
“They didn’t know it was on fire and we had to tell them,” he added.
“I couldn’t hear any alarms going off either.”
But a spokesman for Primark said the fire alarm did activate.
In a statement, he added: “Our Belfast store on Castle Street was safely evacuated this morning (Tuesday) following a fire on the roof.
“Fire services are attending the scene and working to extinguish the fire.”
The Bank Buildings were designed by Sir Robert Taylor and erected by Waddell Cunningham in 1785.
The original bank opened in 1787 under the name of ‘The Bank of the Four Johns’, as all four founders were named John.
After the bank collapsed, the building was used as the residence of the Bishop of Down and Connor.
In 1805, it was converted into a shop, and has remained an outlet for retail ever since. Primark took over the building in 1979.