The whales, which weighed up to 20 tonnes each, had all died by late on Thursday, park ranger Peter Collins told Australian Broadcasting Corp radio.

He said he had confiscated a whale's jawbone and a chainsaw from a man he found near the beach.

"It is very disappointing and a sad moment for these animals to see them lying here on the beach," Collins said.

"It is quite disappointing to see someone capitalizing on their demise."

A spokesman for Western Australia's Conservation and Land Management department said an axe covered in blood and whale tissue was also seized.

He said the department was questioning a man as part of investigations which would also determine whether the jawbone was taken as a souvenir or for sale on the black market.

Local media said the whale's lower jaw weighed up to 88 lbs and included teeth.

The whales were all suffering bad cuts when they were beached after washing across a reef, forcing authorities to warn people to stay out of the water for fear of sharks. This in turn made rescue and then recovery efforts impossible.