More than 120 firefighters have been tackling two huge fires in Manchester city centre - one of which completely destroyed a five-storey building.
The blaze in a commercial building on Dale Street has been brought under control, although crews are continuing to tackle a fire in the block opposite.
An inquiry is yet to begin, but it was initially believed that embers from the first fire sparked the second.
There were also unconfirmed reports a person may have been trapped inside.
The first fire crews on the scene were told some people may have been sleeping rough in the building, but Greater Manchester Police said they did not believe anyone was trapped inside.
Traffic is being disrupted on nearby roads and motorists are advised to avoid the area, which is likely to remain cordoned off for about 24 hours.
At its height, more than 25 fire appliances, police and paramedics were are all at the scene in the Northern Quarter.
The alarm was raised at 0555 BST and the incident quickly escalated.
A number of streets including Dale Street, Lever Street, Hilton Street, Newton Street and part of Oldham Road were closed, leading to chaotic traffic in the surrounding area.
Bill Harrop, Borough Commander for Greater Manchester Fire Service, said: "We managed to bring the fire under control but the building is completely destroyed. There is a real risk that it may collapse.
"There were early reports of a number of people possibly missing but we cannot confirm yet that anyone was inside.
"It is too early to say how the fire started or how it spread. A joint investigation between the fire service and police is under way."
Mr Harrop said flames in the second building had affected the upper floors and the roof, which had partially collapsed.
But although there were fears the building was in danger - at one point firefighters inside were ordered out - he said engineers had declared it structurally safe.
Mr Harrop said the entire block of buildings had been evacuated as a result of the blaze.
He added: "This is an extremely difficult fire. We were struggling for access... this is a very, very difficult incident to tackle."
The fire service is expecting to scale down its operations during the afternoon, but firefighters could remain at the site for a number of days.
Earlier, Greater Manchester Fire Service spokesman Ged Higgins said only the shell of the first building remained - all the internal floors and the roof had been destroyed.
Structural engineers and gas experts are at the scene of the fire, near the busy Piccadilly shopping area, but there is believed to be no risk to the public.
The area is packed with narrow streets and Victorian warehouse buildings which have been converted into retail, commercial and apartment units.
Resident David Lembergh, 38, who has an office and apartment in the second building told the BBC he had a lucky escape because he was staying with his mother.
He said: "I got a call first thing from a fellow resident saying, 'Are you out of the building? Are you out of the building because the roof is on fire.'
"Obviously I got in a panic because I know various other people who live there and I was ringing them and luckily everyone escaped.
"The main thing is nobody is injured, hurt or has been killed but I am slightly concerned all my personal items are secure."
Have you been in the area this morning? Can you tell us anything about the fire? If you have any information you would like to share with the BBC you can do so using the form below:
You can send pictures and video to: email@example.com or to send via MMS please dial +44 (0)7725 100 100.
Do not endanger yourself or others, take any unnecessary risks or infringe any laws.
The BBC may edit your comments and cannot guarantee that all emails will be published.