SYDNEY - At least 150 whales have died in a mass stranding off Tasmania's west coast, Australian authorities said on Sunday, despite the efforts of rescuers who managed to shepherd a small number back to the ocean.

The state government said the number of long-finned pilot whales that had perished had climbed to 150 after a body count on Sunday, almost double the earlier estimate of 80.

The stranded whales were discovered on Saturday and members of the local community and government officials worked to rescue them, but the whales had been badly injured by the rocks.

Department of Primary Industries and Water spokesman Warwick Brennan was quoted in Australian media said rescuers in a boat managed to steer about 30 whales out of the bay.

Pilot whales are among the smaller whales, typically up to about 5 meters (16 ft) in length and dark with a grey underbelly.

Last week, 64 long-finned pilot whales were stranded at Anthony's Beach on Tasmania's north-west coast. Eleven of those whales were rescued and returned to sea.

Mass strandings of whales occur periodically in Australia and New Zealand for reasons that are not entirely understood. Theories include disturbance of echo-location, possibly by interference from sound produced by human activities at sea.