Nineteen pilot whales washed up on a Cape Town beach in South Africa Sunday and seven of them died, sea rescue officials said, prompting a frenzy to save the remaining giant mammals.

"We don't know what might have caused the mass whale stranding, unfortunately seven have died," said Craig Lambinon, the spokesman for the National Sea Rescue Institute.

He said efforts were under way to release the surviving whales back into the sea and to dispose of the seven carcasses.

The scene at Noordhoek beach on the Atlantic coast attracted dozens of curious onlookers who eagerly snapped pictures of the creatures, as rescuers tried to hose down the surviving animals.

Pilot whales are members of the dolphin family and grow up to six metres (20 feet) long.

The reason why they beach themselves is unknown, although scientists speculate it may occur when their sonar becomes scrambled in shallow water.