Investigations are underway to determine the cause of fire that left four people dead and seven others injured at a boarding house in central Cape Town, it said on Saturday.

One of the seven injured people was in a critical condition with facial burns following the Friday incident.

"The inspectors of the Department of Labour have begun working jointly with the Disaster Management Unit of the City of Cape Town to determine the cause of the fire," labour spokesman Page Boikanyo said.

The blaze ripped through the crowded Two Oceans Backpackers on Loop street at 5am on Friday, said Western Cape police spokesperson Superintendent Andre Traut.

Shocked survivors told how they escaped advancing flames by jumping from upper storey windows.

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

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

"The Minister of Labour Membathisi Mdladlana regrets the loss of life, and also wishes to convey his condolences to the bereaved families," said Boikanyo.