Two women died in a fire in a multi-storey building in the Johannesburg CBD on Wednesday morning, the city's fire and emergency management services said.

Spokesperson Percy Morokane said the women, aged between 20 and 25, died of smoke inhalation.

A man who tried to jump from the fifth floor of the burning building was in a critical condition in hospital with a broken leg and a number of other injuries. He was also suffering from smoke inhalation, as were another seven people in a serious condition in hospital.

Some of them had been writing their matric exams when the fire broke out, Morokane said.

A creche on the second floor of the building had been evacuated and all the children accounted for.

Morokane said the blaze started at 11.30am at 101 Embassy Place, in Bree street, between Rissik and Joubert streets, and which houses the Eaglesvale College.

Firefighters believed they had the flames contained to the fifth floor and under control by early afternoon and were checking whether anyone was still inside.

However, the flames started spreading upwards and were consuming the sixth and seventh storeys at 1.30pm.

It was unclear what started the fire.