Three adults and a 12-year-old child were rescued by firefighters using ladders after a blaze broke out in a block of flats.
Eight other people managed to escape by themselves from the tenement in Edinburgh’s Newington area.
Two people were taken to Edinburgh Royal Infirmary suffering from smoke inhalation and ten others were treated at the scene.
Firefighters were called to the flats in Rankeillor Street just after 11pm on Tuesday night after receiving the first of six 999 calls.
The fire was in the basement area of number four, on the corner of the street and Clerk Street.
When they arrived they found a large volume of smoke coming from a fire which spread to a flat next door, a dentist's surgery, and to properties in Clerk Street.
At the height of the incident, more than 40 firefighters were at the scene tackling the blaze, which started in a stairwell.
The Red Cross vehicle, based at Tollcross fire station, was sent to look after the residents of surrounding properties who had to be evacuated.
It was under control by 2am but five firefighters were still at the scene until Wednesday morning damping down the property.
David Lockhart, Community Safety Manager at Lothian and Borders Fire and Rescue Service said: "This highlights the need for residents living in tenement buildings to be aware of the storage of items within their common stair which could be set on fire.
"Make sure that common stairs are keep clear from rubbish or any items which may block an escape route in an emergency. It's also vital that people have a plan of what to do if they discover a fire in their home or stair.
"This is something that the Service can help with through the Home Safety Visit programme where we can also fit a free smoke alarm."
Lothian and Borders Fire and Rescue has launched an investigation.