US beached whale 'had skull fractures'

US scientists say a blue whale that washed ashore had multiple skull fractures.

US scientists say a blue whale that washed ashore had multiple skull fractures. (AAP)

A blue whale that washed ashore on the US west coast had multiple skull fractures that were consistent with a collision with a ship.

The Marine Mammal Center said on Friday that a team including scientists from the California Academy of Sciences and University of California reached the conclusion after studying the carcass.

They already knew that the 20-metre-long male whale suffered blunt force trauma before washing onto a Daly City beach.

Upon closer inspection, the scientists found "extensive" bruising along its spine.

It was the seventh blue whale carcass beached in the last 40 years along the coastline of central and Northern California.

Blue whales are the largest animals in the world, and are endangered. They can grow longer than a basketball court and weigh more than 15 school buses.