Up to 20 people are believed to be trapped under rubble after a shopping centre under construction in South Africa collapsed, officials have said.

Medical response company Crisis Medical said at least three people died and 42 others had been taken to hospital, some with "massive traumatic injuries".

The collapse happened at a construction site in the town of Tongaat, 40km (25 miles) north of the eastern coastal city of Durban. Medical official Neil Powell said "It's a very big construction site, probably about 200m (656ft) long".

Rescuers search the rubble at the scene 

He said most of the injuries were "broken bones, multi-fractures and crush injuries...some are in severe condition, others are mild".

The Emergency Operations Control Centre said the rescue operation is now declared as search and recovery.

Television footage showed police and rescue workers walking over large piles of rubble and twisted metal lying next to a railway track.

It is not clear what caused the three-storey building to collapse, but a deputy mayor in the area said authorities had obtained an injunction a month ago to stop construction at the site.

"There are areas of the law that they did not follow in terms of building of this infrastructure" deputy mayor Nomvuzo Shabalala told broadcaster eNCA.

"We were not aware that they were continuing building."

Chris Botha, a spokesman for the Netcare 911 emergency service, said the second floor of the structure had given way.

"The scene is extremely horrific...concrete big blocks have fallen on to people," he told broadcaster eNCA from the scene.

"The guys are busy using hydraulic rescue equipment to break through the concrete and get to some of the patients."

Mandy Govender, a police spokeswoman, said sniffer dogs were combing the area for survivors. "There's just chunks and chunks of concrete and we don't know what's underneath" she said.

Images: Crisis Medical