Several patients are trapped after the a collapsed at a hospital in Johannesburg, South Africa, emergency service officials said.

The at the public entrance of the Charlotte Maxeke Hospita caved in as construction workers were trying to seal a leak.

Five people were injured and it was not clear how many people were still trapped under the rubble.

Two of the injured were patients, two were construction workers while one person was a hospital staff member.

Footage on social media showed rescue workers digging at the rubble with their bare hands.

"There are several patients trapped. Rescue workers are busy on the scene at the moment trying to ascertain the safety," ER24 spokesman Russel Meiring said.

Eye Witness News quoted sources at the scene saying two people were trapped in the rubble and that one person had been removed. The eNCA television channel said four people had been injured.

Jack Bloom, health spokesman for the Democratic Alliance in Gauteng, said he warned the hospital was "structurally unsound".

Sharing a picture of the collapse on Twitter, he said: "The devastation at Charlotte Maxeke Hospital - I warned years ago that the hospital was structurally unsound."