How once in a decade fire gutted inner-city buildings
WHAT WE KNOW SO FAR
* A century-old, seven-storey former hat factory in Surry Hills had been vacant for four months and was known to regularly house 15 rough sleepers - 13 have confirmed they are safe
* A second building, formerly home to Sydney karaoke bar Ding Dong Dang, was damaged significantly by the blaze
* Plans had been lodged with the local council to convert the two brick-and-timber buildings into a 123-room, two-restaurant hotel at a cost of almost $40 million
* Property manager Reuben, who lives in a neighbouring apartment, told AAP he thought the neglected building was a disaster waiting to happen, saying it "looked like a tinder box".
* More than 120 firefighters from 30 fire trucks battled the blaze, consuming two buildings after it broke about 4pm on Thursday.
* The old factory's roof, floors and parts of its walls collapsed before 5pm, sending red hot bricks tumbling to the streets
* The second building was damaged significantly
* The inferno was a "once in a decade type of fire", Fire and Rescue NSW Acting Commissioner Jeremy Fewtrell said on Friday
* A combination of factors combined to create the "perfect" conditions for a very intense fire, including the structure's age, height and copious amounts of timber framework, Mr Fewtrell said
* The only reported injury was a minor burn suffered by a firefighter
* Firefighters remained on the scene on Friday, dousing hotspots and monitoring charred remains for potential flare ups.
* The police arson squad is leading the probe
* Local locksmith Phu Tang told reporters he spotted a group of high school-aged children running from the building
* Two 13-year-olds handed themselves into police on Thursday night
* Police have urged three or four other young people, who may have been inside the building, to come forward with their parents
THE COMING DAYS
* About 50 residents from two apartment blocks remain locked out on Friday as concerns grow about a bulging wall in the factory
* The integrity of the factory's remaining walls is being assessed by engineers from Public Works NSW and plans for re-entry will be put together in coming days
* Impacted residents are urged to register online with the Red Cross for support
* Among those locked out overnight was a bride due to be married in Hobart on Friday, but firefighters accessed her apartment and retrieved her dress
* A large exclusion zone will remain in place for at least seven days