The death toll from a boarding house fire in central Cape Town remained at four, police said on late Friday afternoon.

There was still a "slight possibility" of more bodies, as the building was still unsafe for investigators, said Superintendent Andre Traut.

The blaze ripped through the old building before dawn on Friday, and shocked survivors told how they escaped advancing flames by jumping from upper storey windows.

Traut said the Loop Street establishment, known as Two Oceans Backpackers, was full to capacity at the time.

Seven people were injured in the blaze, four of them seriously.

"We are awaiting the arrival of our forensic expert for arson cases to investigate the circumstances and determine the cause," he said.

"That is basic procedure because we've got people who died in the fire."

Western Cape health department spokesperson Faiza Steyn said five people, all Somalians, were admitted to Somerset hospital in the city following the blaze.

One was in a critical condition with facial burns, and would be transferred to Tygerberg hospital's burns unit for further care.

One was under observation, and the other three were being treated for minor injuries and would be discharged.

A city disaster management official said though survivors would be assisted with transport, they would have to find their own accommodation.

Welfare organisations had provided blankets and hot meals, and an NGO had offered to help them rebuild documentation lost in the fire.

Many of the former residents of the building are foreign nationals.