Video footage shows the two girls, believed to be aged 17 and six, jumping from a window into the arms of waiting neighbours, as the flames fanned ever-higher from the roof and the corridors filled with smoke.

Twenty-nine people lost their homes when the blaze engulfed the Morgan's Landing apartment block in Sandy Springs, Georgia on Tuesday afternoon, a local news channel reported.

The crew of 11 Alive television news captured the girls screaming for help after breaking a glass window pane above the front porch, before leaping into the arms of two men standing below.

One of those men, Thomas Lemon, said he heard the young women pleading for help and then ran to the burning building, instructing them to smash the glass.

"I could hear banging on the window and I ran upstairs and told them to break the window and they broke the window," he told FOX News.

"The older one was 17 and she jumped down and I looked up and a six-year-old was jumping down and I heard the glass cut her leg and her leg was gashed wide."

The two girls were taken to hospital and were reportedly so disoriented they could initially not recall their mother's mobile phone number. Another woman was treated at the scene and released.

A young girl affected by the fire was crying at the scene, the Daily Mail reported. "The most important thing is that we got out," she said.

Red Cross officials assisted residents who were left homeless by the fire and local authorities commenced an investigation into the cause of the blaze.

On Thursday, Sandy Springs Fire and Rescue said the likely cause was improper disposal of a cigarette.