A fire at a homeless hostel is being investigated.
The blaze started on the first floor of the YMCA in Old Steine, Brighton, at about 4.50pm.
The Victorian building, which is home to about 60 people, was badly damaged by smoke and flames.
The fire was contained by 6pm but firefighters continued to work to douse flare-ups in wall cavities and try to find 12 people they said were missing.
At 8pm East Sussex Fire and Rescue Service group commander Mark Rist said: “We are completing the final checks of the building but we are reasonably confident all the missing residents are
About 60 people living in the YMCA were collected by Brighton and Hove City Council and taken to temporary shelter.
About 30 people were taken to Hove Town Hall for the night.
Others were being housed in hotels and bed and breakfast accommodation.
A council spokesman said: "We have a statutory duty to ensure people are housed, particularly vulnerable people.
"Our staff are going to take care of them through the night. Tomorrow they'll be relocated in temporary accommodation."
Members of the public said they saw smoke billowing from the windows of the YMCA late in the afternoon.
The fire spread upwards onto the second floor towards the roof.
Most people living in the building were outside by the time firefighters arrived.
They gathered on the grass near the Dolphin fountain on the other side of the road as firefighters arrived.
Witnesses said the smoke seemed to be coming from the back of the building.
Resident Daniel Coe said the fire had spred to his room on the top floor of the building.
“Mr Coe, 25, said: “I was downstairs and I heard the fire alarm. I thought it was a test.
“Then I could smell smoke.
“All of my stuff was in there. I don’t know where I’m going to stay.”
Another resident, who did not want to be named, said he had only been released from Lewes prison yesterday morning.
He said: “I’ve been away three years and just come back today.
“I put my stuff in the room then went to sign on at probation and when I got back it was like this.
“Everything I own in the world was in there, my clothes, my money, pictures of my kids.”
Buildings on either side of the YMCA were also evacuated.
About 12 fire engines, three ambulances and police were still working at the scene at 7.20pm.
Sussex fire services were stretched because of a number of floodings at houses and road drains following storms in the afternoon.
Firefighters from Barcombe and Lewes were taking part in the operation as well as crews from across the city.
A spokeswoman for Sussex Police said: "An investigation into the cause and seat of the fire, which has left the building badly damaged, will take place in due course."