An overnight fire killed 12 residents of a home for the mentally disabled in a town east of Johannesburg, the emergency services department said on Monday.

Another 27 were injured in the fire at the Struitsbuild Care Centre in the town of Springs, municipal emergency spokesman Rogers Mamaila said.

Three dozen firefighters rushed to the scene after midnight, Mamaila told Radio 702.

"We managed to take them out and now we are busy taking them to hospital but most of them for minor injuries, burn injuries and smoke inhalation," Mamaila said.

About 27 residents were taken to area hospitals, he said.

The management of the privately-owned centre believe that the fire might have been caused by a cigarette.

All those who died were women aged between 30 and 45. The wing which was gutted by the fire accommodated 59 people.

Family members of the dead have began arriving at the scene and are receiving counselling.

"They are being told what has happened and are being taken to identify their loved ones," said Sello Mokoena, the Gauteng health department spokesman.

Last August, 22 elderly people died at a retirement home in Nigel on the southeastern outskirts of Johannesburg.

In February a deadly fire killed 13 children and two adults at an orphanage in KwaZulu Natal.